Find the Perpendicular Line: Solving 3y=4x-y through Point (-3,-15)

Question

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

Solution Steps

00:00 Find the algebraic representation of the function
00:03 Isolate Y
00:13 This is the equation of the perpendicular function
00:20 This is the slope of the perpendicular function
00:24 The product of slopes of perpendicular lines is (-1)
00:32 Substitute the slope and solve to find the second slope
00:42 This is the slope of our function
00:47 A point through which our function passes according to the given data
00:50 We'll use the line equation
00:54 Substitute the point according to the given data
00:59 Substitute the slope, and solve to find the intersection point (B)
01:15 Isolate the intersection point (B)
01:21 This is the intersection point with the Y-axis
01:24 Now let's substitute the intersection point and slope in the line equation
01:44 Arrange the equation
01:50 And this is the solution to the problem

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