Question

Julio sells hand-painted skateboards. The graph shows how the price of a skateboard is related to the amount of time Julio spends painting it. Julio says the equation of the line is y = 10x + 15. Explain what mistake Julio made. Write the correct equation for Julio’s line.

I really need help

Answer 1

Take 2 points

• (0,10)
• (2,40)

`\\ \sf\longmapsto m=(40-10)/(2-0)=(30)/(2)=15`

Equation of line in point slope form

`\\ \sf\longmapsto y-y_1=m(x-x_1)`

`\\ \sf\longmapsto y-10=15(x)`

`\\ \sf\longmapsto 15x-y+10=0`

Answer 2

• y = 15x + 10

Explanation:

Use two points on the line to find the equation:

• (0, 10), (2, 40)

Find the slope:

• m = (40 - 10)/2 = 15

The line is:

• y = 15x + 10

The mistake was the swapped slope and y-intercept values.