15 y is directly proportional to (x - 1) 2 . when x = 5, y = 4.
find y when x = 7.

y = 9

Step-by-step explanation:

Given y is directly proportional to (x - 1)² then the equation relating them is

y = k(x - 1)² ← k is the constant of proportionality

To find k use the condition x = 5 when y = 4

k = = = = , thus

y = (x - 1)² ← equation of proportion

When x = 7, then

y = × 6² = × 36 = 9