Determine the Equation of a Line: Slope of 1/2 and Passing Through (5, 17.5)

Point-Slope Form with Mixed Number Coordinates

A line has a slope of 12 \frac{1}{2} and passes through the point (5,1712) (5,17\frac{1}{2}) .

Which expression corresponds to the line?

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the algebraic representation of the function
00:03 We'll use the linear equation
00:09 We'll substitute the point according to the given data
00:18 We'll substitute the line's slope according to the given data
00:21 We'll continue solving to find the intersection point
00:32 We'll isolate intersection point B
00:39 This is the intersection point with the Y-axis
00:42 Now we'll substitute the intersection point and slope in the linear equation
00:49 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

A line has a slope of 12 \frac{1}{2} and passes through the point (5,1712) (5,17\frac{1}{2}) .

Which expression corresponds to the line?

2

Step-by-step solution

To determine the line's equation, we'll follow these steps:

  • Use the point-slope form of a line, given by yy1=m(xx1) y - y_1 = m(x - x_1) .
  • Substitute m=12 m = \frac{1}{2} , x1=5 x_1 = 5 , and y1=1712 y_1 = 17\frac{1}{2} into the equation.
  • Solve for y y to put the equation in slope-intercept form.

Now, let's work through the steps:

Given the point (5,1712) (5, 17\frac{1}{2}) and slope m=12 m = \frac{1}{2} , our start point is the point-slope form:
y1712=12(x5) y - 17\frac{1}{2} = \frac{1}{2}(x - 5) .

Convert the mixed number to an improper fraction: 1712=352 17\frac{1}{2} = \frac{35}{2} .

Thus, the equation becomes y352=12(x5) y - \frac{35}{2} = \frac{1}{2}(x - 5) .

Distribute the slope on the right-hand side:
y352=12x52 y - \frac{35}{2} = \frac{1}{2}x - \frac{5}{2} .

To solve for y y , add 352 \frac{35}{2} to both sides:
y=12x52+352 y = \frac{1}{2}x - \frac{5}{2} + \frac{35}{2} .

Combine the fractions on the right-hand side:
y=12x+302 y = \frac{1}{2}x + \frac{30}{2} , which simplifies to y=12x+15 y = \frac{1}{2}x + 15 .

Therefore, the equation of the line in slope-intercept form is y=12x+15 y = \frac{1}{2}x + 15 .

Comparing this with the multiple-choice options, the correct answer is:

y=12x+15 y = \frac{1}{2}x + 15

3

Final Answer

y=12x+15 y=\frac{1}{2}x+15

Key Points to Remember

Essential concepts to master this topic
  • Form: Use point-slope formula y - y₁ = m(x - x₁)
  • Technique: Convert mixed number 17½ to improper fraction 35/2
  • Check: Substitute point (5, 17.5) into final equation: 17.5 = ½(5) + 15 ✓

Common Mistakes

Avoid these frequent errors
  • Leaving mixed numbers unconverted
    Don't work with 17½ directly in calculations = arithmetic confusion and wrong y-intercept! Mixed numbers make distribution and combining fractions extremely difficult. Always convert to improper fractions (17½ = 35/2) before substituting into formulas.

Practice Quiz

Test your knowledge with interactive questions

Look at the linear function represented in the diagram.

When is the function positive?

–8–8–8–7–7–7–6–6–6–5–5–5–4–4–4–3–3–3–2–2–2–1–1–1111222333444555666777888–5–5–5–4–4–4–3–3–3–2–2–2–1–1–1111222333000

FAQ

Everything you need to know about this question

Why do I need to convert the mixed number to an improper fraction?

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Converting 1712 17\frac{1}{2} to 352 \frac{35}{2} makes the algebra much easier! You can't easily subtract or add mixed numbers in equations, but fractions work smoothly with the point-slope formula.

Can I use slope-intercept form directly instead?

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You could try y=mx+b y = mx + b directly, but you'd still need to find the y-intercept b. The point-slope method is actually faster when you have a specific point!

How do I remember which number goes where in point-slope form?

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In yy1=m(xx1) y - y_1 = m(x - x_1) , the subscript 1 values come from your given point (x₁, y₁). So for point (5, 17½), you get x₁ = 5 and y₁ = 17½.

What if my final answer doesn't match any of the choices?

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Double-check your fraction arithmetic! The most common error is in combining fractions: 52+352=302=15 -\frac{5}{2} + \frac{35}{2} = \frac{30}{2} = 15 . Make sure you have the same denominator before adding.

Can I check my answer by plugging in the given point?

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Absolutely! Substitute (5, 17.5) into y=12x+15 y = \frac{1}{2}x + 15 : Does 17.5=12(5)+15 17.5 = \frac{1}{2}(5) + 15 ? Yes: 17.5=2.5+15=17.5 17.5 = 2.5 + 15 = 17.5

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