Answer:
c). y + x = 0
Step-by-step explanation:
The locus is a line perpendicular to the line connecting the 2 points and passing through the centre of the line.
The mid-point of the line connecting the given points is:
(a + b + a - b)/2 , (a - b + a + b) / 2
= (a, a)
It's slope = (a + b)- (a - b) / (a - b)- (a + b)
= 2b/ -2b
= -1
So the slope of the line we want is -1/(-1) = 1.
Using the point-slope form of a line:
y - y1 = m(x - x1)
y - a = 1(x - a)
y - a = x - a
x + y = 0
7. D
8. D
9. D
10.C
for 7 & 8 you use the equation

your points are (3,8) & (9,5)
so you plug the numbers in
y2= 5
y1=8
x2=9
x1=3
you subtract them get a fraction and that is your slope
9 & 10
use the equation

plug you numbers in for y1 and x2 m is your slope plug it in and that is your equation
Change the mixed numbers into simple fractions:
-9/4-(-67/8)
Find the common denominator and subtract:

So your answer is H
Hope that helps