Answer:
y = 18
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 = 50 when x = 5
50 = k × 5² = 25k ( divide both sides by 25 )
2 = k
y = 2x² ← equation of proportion
When x = 3 , then
y = 2 × 3² = 2 × 9 = 18
