Question

y varies directly as the square of x. When x = 1, y = 3. What is the value of y when x = 3?

Answer 1

y varies directly to the square of x, we can introduce a constant k to equate both of them,\[y=kx ^{2}\]so given (1,3) solve for the k, then rewrite the equation with the value of k.
next substitute your new x into the equation to obtain your y