Question

If y varies directly as x^2 and y=12 when x=2, find y when x=5

Answer 1

`y=ax^2\\\\y=12\ \ \ and\ \ \ x=2\ \ \ \Rightarrow\ \ \ 12=a\cdot 2^2\ \ \ \Rightarrow\ \ \ a= (4)/(12)= (1)/(3) \\\\y=(1)/(3) x^2\\\\x=5\ \ \ \Rightarrow\ \ \ y=(1)/(3) \cdot5^2=(25)/(3) =8(1)/(3)`