ACT Preparation / Unit 11 ACT 1004 short lesson, about 20 seconds
The Quadratic Formula
Captions available
The idea
The solutions of ax² + bx + c = 0 are x = (−b ± √(b² − 4ac))/(2a). The formula works for every quadratic, factorable or not.
In practice
2x² + 3x − 2 = 0: x = (−3 ± √(9 + 16))/4 = (−3 ± 5)/4, so x = 1/2 or −2.
Where people slip
Divide the whole numerator by 2a.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Something wrong in this lesson? Flag it · Sources for ACT Preparation