Question

How do you factor `-x^2+10x-21`?

Answer 1

-(x - 3)(x - 7)

Explanation:

`y = - 1(x^2 - 10x + 21) .`
To factor the trinomial in parentheses, find 2 numbers knowing sum (-10 = b) and product (c = 21).
They are the numbers inside the factor pair (-3, -7) of (21).
y = -(x - 3)(x - 7)