Question

What is the missing y-coordinate that would produce a slope of 3, if a line were drawn through the points left-parenthesis 4 comma 5 right-parenthesis and left-parenthesis 8 comma y right-parenthesis?

Answer 1

Since the slope of a line is $\frac{y_{2}-y_{1} }{ x_{2}-x_{1} }$
And 2 points of the line are given, (4,5) and (8,y) we can substitute those values into our equation.

$\frac{y-5}{8-4} = \frac{y-5}{4}$

Since the slope of the line is 3,
$\frac{y-5}{4} = 3$
Multiplying both sides by 4 would give us:

y-5=12
y=17

Therefore the missing y value equals 17.