ACT Preparation / Unit 11 ACT 1009 short lesson, about 20 seconds
Sum and Product of the Roots
Captions available
The idea
For ax² + bx + c = 0, the roots r and s satisfy r + s = −b/a and rs = c/a.
In practice
2x² − 10x + 12 = 0: the roots sum to 5 and multiply to 6; they are 2 and 3.
Where people slip
Mind the sign of the sum: it is −b/a, not b/a.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Unlocks
Something wrong in this lesson? Flag it · Sources for ACT Preparation