Question

What can you add to `x^2-9x` to get a perfect square trinomial?

Answer 1

`20.25`

Explanation:

In a perfect square, the equation is `ax^2+bx+c`, where `abs(b) = 2asqrt(c)`. Therefore, to find `c`, plug in `a` and `b`.

`abs(b)=2asqrt(c)`

`abs(-9) = 2*1*sqrt(c)`

`9 = 2*sqrt(c)`

`4.5 = sqrt(c)`

`20.25 = c`