9. Perfect Squares
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To factor a perfect square trinomial, the first and last terms have to be perfect squares.
Perfect Square?: Yes Factored Form: (9x-5)^2
To determine if an expression is a perfect square trinomial, we need to ask ourselves three questions.
| Is the first term a perfect square? | 81x^2=( 9x)^2 ✓ |
| Is the last term a perfect square? | 25= 5^2 ✓ |
| Is the middle term twice the product of 5 and 9x? | 90x= 2* 5* 9x ✓ |
As we can see, the answer to the three questions above is yes! Therefore, we can write the trinomial as the square of a binomial. Note there is a subtraction sign in the middle. 81x^2-90x+25 ⇔ ( 9x- 5)^2
After expanding and simplifying, the result is the same as the given expression. Therefore, we can be sure our solution is correct!