Equation of a Straight Line: Point-Slope Form of a Line

Examples with solutions for Equation of a Straight Line: Point-Slope Form of a Line

Exercise #1

Straight line passes through the point (6,14) (6,14) and parallel to the line x+3y=4x+9 x+3y=4x+9

Video Solution

Step-by-Step Solution

To solve the problem of determining the equation of the line parallel to x+3y=4x+9x + 3y = 4x + 9 and passing through point (6,14)(6, 14), we will follow these steps:

  • Step 1: Rearrange the given line to find its slope.
  • Step 2: Use the slope and the given point to apply the point-slope form of a line.
  • Step 3: Convert the equation into the slope-intercept form for clarity.

Let's perform each step:

Step 1: First, the equation x+3y=4x+9x + 3y = 4x + 9 simplifies to find the slope. Subtract xx from both sides to get 3y=3x+93y = 3x + 9. By dividing everything by 3, this gives y=x+3y = x + 3. Therefore, the slope, mm, is 1.

Step 2: Given that parallel lines share the same slope, the slope of the desired line is also 1. Applying the point-slope form: y14=1(x6)y - 14 = 1(x - 6).

Step 3: Simplifying this equation yields y14=x6y - 14 = x - 6. Further rearranging gives y=x+8y = x + 8.

Thus, the equation of the line parallel to the given line and passing through (6,14)(6, 14) is y=x+8 y = x + 8 .

Answer

y=x+8 y=x+8

Exercise #2

Choose the function for a straight line that passes through the point (2,13) (-2,-13) and is parallel to the line 4+y=5x6 -4+y=5x-6 .

Video Solution

Step-by-Step Solution

First, write out the line equations:

4+y=5x6 -4+y=5x-6

y=5x+46 y=5x+4-6

y=5x2 y=5x-2

From here we can determine the slope:

m=5 m=5

We'll use the formula:

y=mx+b y=mx+b

We'll use the point (2,13) (-2,-13) :

13=5×2+b -13=5\times-2+b

13=10+b -13=-10+b

3=b -3=b

Finally, substitute our data back into the formula:

y=5x+(3) y=5x+(-3)

y=5x3 y=5x-3

Answer

y=5x3 y=5x-3

Exercise #3

Straight line passes through the point (5,12) (-5,12) and parallel to the line 5y5x=15 5y-5x=15

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Determine the slope of the given line 5y5x=155y - 5x = 15.
  • Step 2: Use this slope and the point (5,12)(-5, 12) in the point-slope form.
  • Step 3: Rearrange the equation to find the required line's equation.

Let's work through each step:

Step 1: Determine the slope of the given line.
First, convert the equation 5y5x=155y - 5x = 15 to slope-intercept form (y=mx+by = mx + b):

Divide every term by 5 to simplify:
5y=5x+155y = 5x + 15
y=x+3y = x + 3

The slope (mm) of this line is 11.

Step 2: Use the point-slope form with the given point and slope.
We have a point (5,12)(-5, 12) and a slope m=1m = 1. The point-slope form is:

yy1=m(xx1)y - y_1 = m(x - x_1)
Substitute y1=12y_1 = 12, x1=5x_1 = -5, and m=1m = 1:
y12=1(x+5)y - 12 = 1(x + 5)

Simplify the equation:
y12=x+5y - 12 = x + 5

Step 3: Rearrange to get the solution.
Rearrange the equation:
y=x+5+12y = x + 5 + 12
y=x+17y = x + 17

We want to express this in the form of one of the given choices:
yx=17y - x = 17.

Therefore, the solution to the problem is yx=17y - x = 17.

This matches the final answer choice given in the problem, confirming our solution is correct.

Answer

yx=17 y-x=17

Exercise #4

Straight line passes through the point (0,1) (0,1) and parallel to the line 2(y+1)=16x 2(y+1)=16x

Video Solution

Step-by-Step Solution

To solve for the equation of the line parallel to 2(y+1)=16x 2(y+1)=16x that passes through the point (0,1) (0,1) , follow these steps:

  • Step 1: Convert the given line's equation to slope-intercept form. Start with 2(y+1)=16x 2(y+1) = 16x .
  • Step 2: Distribute and simplify to get 2y+2=16x 2y + 2 = 16x , which rearranges to 2y=16x2 2y = 16x - 2 .
  • Step 3: Solve for y y by dividing everything by 2: y=8x1 y = 8x - 1 . Hence, the slope m m is 8.
  • Step 4: Use the slope of 8 and the point (0,1) (0,1) in the point-slope form of a line equation:
    yy1=m(xx1)\quad y - y_1 = m(x - x_1)
  • Step 5: Substitute the point (0,1) (0,1) and the slope 8 8 :
    y1=8(x0)\quad y - 1 = 8(x - 0)
  • Step 6: Simplify the expression
    y1=8x\quad y - 1 = 8x
  • Step 7: Rewrite the equation to achieve the desired form by moving 1 to the other side:
    y=8x+1\quad y = 8x + 1
  • Step 8: To match the expected form, rewrite
    y8x=1 y - 8x = 1

Therefore, the equation of the line that meets the criteria is given by y8x=1 y - 8x = 1 , corresponding to choice 3.

Answer

y8x=1 y-8x=1

Exercise #5

A line passes through the point (2,9) (2,9) and is perpendicular to the line y=15x+3 y=-\frac{1}{5}x+3 .

Choose the corresponding function.

Video Solution

Step-by-Step Solution

To solve this problem, follow these steps:

Step 1: Identify the slope of the given line.

The given line is y=15x+3 y = -\frac{1}{5}x + 3 . Here, the slope (m m ) is 15-\frac{1}{5}.

Step 2: Determine the slope of the perpendicular line.

For lines to be perpendicular, the product of their slopes must equal 1-1. Hence, if m1=15 m_1 = -\frac{1}{5} is the slope of the given line, the slope (m2 m_2 ) of the line perpendicular to it can be found using:

m1×m2=1 m_1 \times m_2 = -1 , which implies:

15×m2=1-\frac{1}{5} \times m_2 = -1.

Solve for m2 m_2 to get:

m2=5 m_2 = 5 .

Step 3: Use the point-slope form to find the equation of the line.

The line passes through point (2,9)(2, 9), and we have determined m2=5 m_2 = 5 .

Using the point-slope form yy1=m(xx1) y - y_1 = m(x - x_1) , substitute m=5 m = 5 , x1=2 x_1 = 2 , y1=9 y_1 = 9 :

y9=5(x2) y - 9 = 5(x - 2) .

Step 4: Simplify the equation.

Distribute the 5:

y9=5x10 y - 9 = 5x - 10 .

Add 9 to both sides to solve for y y :

y=5x1 y = 5x - 1 .

Therefore, the equation of the line we are looking for is y=5x1\boxed{y = 5x - 1}.

Answer

y=5x1 y=5x-1

Exercise #6

Which function represents a straight line that passes through the point (3,15) (-3,-15) and is perpendicular to the line
3y=4xy 3y=4x-y ?

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Rearrange the given line equation to standard slope-intercept form.
  • Step 2: Determine the slope of the perpendicular line.
  • Step 3: Use the point-slope form to find the equation of the desired line.

Now, let's work through each step:

Step 1: The given line equation is 3y=4xy3y = 4x - y. First, simplify this equation:

3y=4xy 3y = 4x - y

Add yy to both sides to consolidate yy:

3y+y=4x 3y + y = 4x

4y=4x 4y = 4x

Divide both sides by 4:

y=x y = x

The slope mm of this line is 1.

Step 2: Since the line we want is perpendicular to this line, the slope m1m_1 of the desired line should satisfy:

m×m1=1 m \times m_1 = -1

Given m=1m = 1, we have:

1×m1=1 1 \times m_1 = -1

So, m1=1m_1 = -1.

Step 3: Use the point-slope form of a line yy1=m(xx1) y - y_1 = m(x - x_1) with point (3,15)(-3, -15) and slope 1-1:

y(15)=1(x(3)) y - (-15) = -1(x - (-3))

Simplify the equation:

y+15=1(x+3) y + 15 = -1(x + 3)

Expand:

y+15=x3 y + 15 = -x - 3

Subtract 15 from both sides:

y=x315 y = -x - 3 - 15

y=x18 y = -x - 18

Rearrange to the standard form:

y+x=18 y + x = -18

The equation of the line that passes through (3,15)(-3, -15) and is perpendicular to 3y=4xy3y = 4x - y is:

y+x=18 y + x = -18

Answer

y+x=18 y+x=-18

Exercise #7

Which function represents a straight line that passes through the point (0,0) (0,0) and is perpendicular to the line y2x=2y y-2x=2y ?

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Simplify the given equation to find its slope.
  • Determine the slope for the perpendicular line using the negative reciprocal.
  • Write the equation of the line through the origin with this slope.

Let's work through each step:
Step 1: The original line is given by the equation y2x=2y y - 2x = 2y . Simplifying, we subtract y y from both sides to get 2x=y -2x = y or, equivalently, y=2x y = -2x . Here, the slope m1=2 m_1 = -2 .

Step 2: For the line to be perpendicular, its slope m2 m_2 must satisfy m1m2=1 m_1 \cdot m_2 = -1 . Thus, we have 2m2=1-2 \cdot m_2 = -1, yielding m2=12 m_2 = \frac{1}{2} .

Step 3: The equation of the line with this slope that passes through the origin is of the form y=mx y = mx . Substituting the slope 12 \frac{1}{2} , we have y=12x y = \frac{1}{2}x .

Therefore, the function representing the straight line through the origin and perpendicular to the given line is y=12x y = \frac{1}{2}x , which corresponds to choice 1.

Answer

y=12x y=\frac{1}{2}x

Exercise #8

Which function describes a straight line that passes through the point (7,2) (7,2) and is perpendicular to the line 3y=x+12 3y=x+12 ?

Video Solution

Step-by-Step Solution

To solve this problem, we need to determine the equation of a line passing through the point (7,2) (7, 2) and perpendicular to the given line 3y=x+12 3y = x + 12 . We can achieve this by following a systematic approach:

  • Step 1: Identify the slope of the given line

We start by rewriting the equation of the given line 3y=x+12 3y = x + 12 in slope-intercept form, y=mx+b y = mx + b , where m m is the slope. To do this, we divide each side of the equation by 3:

y=13x+4 y = \frac{1}{3}x + 4

Thus, the slope m1 m_1 of the given line is 13 \frac{1}{3} .

  • Step 2: Determine the slope of the perpendicular line

Two lines are perpendicular if the product of their slopes is 1-1. Therefore, if the slope of the line we are looking for is m2 m_2 , then:

m1×m2=1 m_1 \times m_2 = -1

Substituting the value of m1 m_1 :

13×m2=1 \frac{1}{3} \times m_2 = -1

Solving for m2 m_2 , we find:

m2=3 m_2 = -3

  • Step 3: Use the point-slope form to find the equation of the perpendicular line

Now that we know the slope of the perpendicular line is 3-3 and it passes through the point (7,2) (7, 2) , we can use the point-slope form of a line:

yy1=m(xx1) y - y_1 = m(x - x_1)

Here, m=3 m = -3 and the point is (x1,y1)=(7,2) (x_1, y_1) = (7, 2) , so:

y2=3(x7) y - 2 = -3(x - 7)

Expanding this equation to solve for y y , we get:

y2=3x+21 y - 2 = -3x + 21

Adding 2 to both sides to isolate y y , we have:

y=3x+23 y = -3x + 23

Thus, the equation of the line that passes through the point (7,2) (7, 2) and is perpendicular to the line 3y=x+12 3y = x + 12 is y=3x+23 y = -3x + 23 .

The correct answer to this problem is therefore y=3x+23 y = -3x + 23 .

Answer

y=3x+23 y=-3x+23