Question

What is the answer to this

Find y when x=9 if y varies directly as the square of x and y=245 when x=7

Answer 1

The most general function here would be y = kx^2.
Let y=245 and x=7 to find the value of the constant of proportionality k:

245 = k(7)^2, or 49k = 245, or 5.

Then the specific function that applies here is y = 5x^2.