Question

Y is directly proportional to x squared. if y=12 when x=2 find x when y=48

Answer 1

x = 4

Explanation:

y = kx²

NOTE: k is constant for proportionality

putting values for x and y

if x is 2

and y is 12

12 = k(2)²

12 = k4

12 = 4k

divide both sides by coefficient of k

12÷4 = 4k ÷ 4

k=3

substitute 3 for k

therefore when

y is 48

and k is constant 3

then x will be:

48=3x²

divide both sides by coefficient of x²

48 divide by 3 = 3x² divide by 3

16=x²

take the square root of both sides

√16 = √x²

x = 4