Question

Factor 3x2 - x - 10

Answer 1

maria,

do you know the "ac" method? It is one way of factoring this.

Answer 2

what is the ac method?

Answer 3

3x^2 - x - 10

3x^2 - 6x + 5x - 10

(3x^2 - 6x) + (5x - 10)

3x(x - 2) + (5x - 10)

3x(x - 2) + 5(x - 2)

(3x + 5)(x - 2)


So 3x^2 - x - 10 completely factors to (3x + 5)(x - 2)

Answer 4

Note: you multiply the coefficient of the first term 3 by the last term -10 to get -30

Then you find two numbers that multiply to -30 and add to -1. These two numbers are -6 and 5

Answer 5

So we rewrite -x as -6x+5x and then we factor by grouping

Answer 6

what jim just described is the "ac" method