Question

3. Given 4x – 8y = 8:

A) Transform the equation into slope-intercept form.
B) Find the slope and y-intercept of the line.
C) Find the equation, in point-slope form, of the line that is perpendicular to this line and passes through the point (1, 2).

Answer 1

slope-intercept form is y = mx + b, so to turn that equation into slope-intercept you'll need to get y alone

4x - 8y = 8 --- subtract 4x
-8y = 8 - 4x --- divide by -8
y = -1 + (1/2)x --- reorder to match "mx + b"
y = (1/2)x - 1

in y = mx + b, "m" is the slope and "b" is the y-intercept. so for part B, your slope is (1/2) and your y-intercept is (-1). take the sign with you.

for part C, you'll need to know point-slope form: (y - y1) = m(x - x1)
you'll also need to be aware that "perpendicular" lines have a slope that is the opposite reciprocal of the original line.

the original slope is (1/2). change the sign to negative and form a reciprocal: your new slope is -2. plug that into your point-slope form

(y - y1) = m(x - x1)
(y - y1) = (-2)(x - x1)

and lastly, plug in your given point: (1, 2)

y - 2 = (-2)(x - 1)

so, just to look a little neater without all of the work:
A) y = (1/2)x - 1
B) m = (1/2), b = -1
C) y - 2 = (-2)(x - 1)