Question

I'm confuse with these questions

Answer 1

8 a) y=x² stretched vertically by 8

That means (0,0) stays (0,0),  and (1,1) becomes (1,8) and (-1,1) becomes (-1,8)

Answer: y = 8x²

8 b) y=x² compressed vertically by 1/5

Answer: y = (1/5) x²

9.

y = ax² + k through (-1,3) and (3,-13)

That means

3 = a (-1)² + k

-13 = a (3²) + k

Subtracting,

16 = a - 9a = -8a

a = -2

3 = -2 + k

k = 5

y = -2x² + 5

Check:

-2(-1)^2 + 5 = 3, good

-2(3)^2+5 = -18 + 5 = -13, good

Answer: a = -2, k = 5