Factoring x² − bx + c worksheets

x² − 9x + 20 factors into (x − 4)(x − 5) — two negative numbers that multiply to 20 and add to −9. These free printable worksheets drill the both-negative case on its own.

Factoring x² − bx + c
Factoring x² − bx + c worksheet — x² − bx + c, both negative, free printable with answer key

The answer key prints on a separate page.

What's on this sheet

Factoring x² + bx + c is a search for two numbers that multiply to c and add to b, and this sheet fixes both signs so the search has a shape. When c is positive and b is negative, the two numbers are both negative: they multiply to a positive and add to a negative. Knowing that before you start turns a hunt into a short check of a few pairs.

Why this sheet works

The middle term is where the sign lands. Both numbers of the pair are negative, so (x − 4)(x − 5) gives −4x and −5x, which add to the −9x in the middle, and the +20 is negative times negative. A child who writes (x + 4)(x + 5) has the product right and the sum wrong, which is exactly the mistake this narrow sheet is built to surface.