Round each number to the nearest tens hundreds and thousands

If f(x) = 2x - 6 and g(x) = 3x + 9, find (f - g)(x). a. (f-g)(x) = x + 15 o o b. (f- g)(x) = -x - 15 o c. (f- g)(x) = 5x + 3 o d. (f- g)(x) = -x+3 submit

If y varies directly as x2 and y=6 when x=6, find the constant of variation.

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?