Question

Factor the trinomial by grouping. -

5x² - 28x+15
a. Find two numbers whose product is 5.15= 75 and whose sum is - 28.
b. Write - 28x using the factors from part (a).
c. Factor by grouping.

Answer 1

a. The two numbers whose product is 75 and whose sum is -28 are -25 and 3.

b. -28x = -25x + 3x

c. -5x² - 25x + 3x + 15

= -5x(x-5) + 3(x-5)

= (3x-15) + (-5x+25)

= (-5x+3x) + (25-15)

= -2x +10

The trinomial -5x² - 28x + 15 can be factored by grouping as (-2x+10)