Question

y varies directly as the square of x. When x = 4, y = 32. Find x when y = 18.

x = ±3
x = ±8
x = ±10
x = ±26

Answer 1

its like this..

\[y \alpha x^2\]
=> y=kx^2

if x=4 then y=32
put it in above relation to find k i.e.

32=k(4)^2

=>32=16k
=>k=2

so if y=18 then..

18=2x^2
=>x^2=9=>x=+-3

so opton A is right ans.