How do you factor completely #−7x^2 + 14x − 21#?
f(x) = -7y = -7(x^2 - 2x + 3)
D = d^2 = b^2 - 4ac = 4 - 12 = -8.
Since D < 0, the trinomial in parentheses can't be factored.
NOTE. We can factor f(x) by using the 2 complex roots.
The factored form will be: