ACT Preparation / Unit 11 ACT 1003 short lesson, about 20 seconds
Completing the Square
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The idea
To complete the square in x² + bx, add (b/2)² to both sides; the left side becomes (x + b/2)².
In practice
x² + 6x = 7 becomes x² + 6x + 9 = 16, so (x + 3)² = 16 and x = 1 or −7.
Where people slip
The leading coefficient must be 1 first; divide through if it is not.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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