Answer:
d
Step-by-step explanation:
Given y is directly proportional to x² then the equation relating them is
y = kx² ← k is the constant of proportion
To find k use the condition y = when x =
, then
= k(
)² =
k ( multiply both sides by 8 )
1 = 2k ( divide both sides by 2 )
k =
y = x² ← equation of proportion
When y = , then
=
x² ( multiply both sides by 2 )
9 = x² ( take the square root of both sides )
x = ± = ± 3
with positive value x = 3 → d