Question

write the equation of the line, in slope intercept form, through (2,-4) and perpendicular to x-2y=7

Answer 1

y = -2x

Answer 2

how did you get that?

Answer 3

hmm perpendicular slope will be -2

Answer 4

y = -2x + c
determine c by putting in the point (2,-4)

Answer 5

line has form y=mx+b

we know y=mx+b is perpendicular to x-2y=7
what is the slope of x-2y=7?
solve x-2y=7 for y
x-7=2y
y=x/2-7/2

slope is 1/2

so line perpendicular to y=x/2-7/2 would have slope -2

so now we know we have a line in the form y=-2x+b

but we also want to know what line goes through (2,-4)

so we plug that into find b

-4=-2(2)+b
-4=-4+b
add 4 to both sides
0=b

so the line is y=-2x

Answer 6

Perfect !!