ACT Preparation / Unit 8 ACT 0712 short lesson, about 20 seconds
Perfect-Square Trinomials
Captions available
The idea
A perfect-square trinomial is a² + 2ab + b² = (a + b)²: the first and last terms are squares, and the middle is twice their product.
In practice
x² − 10x + 25 = (x − 5)², since 2 × x × 5 = 10x.
Where people slip
The sign inside the square matches the middle term's sign.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
Builds on
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