7.4 Factor Perfect Square Trinomials

Factor:   36 g 2 + 60 g + 25

[1.] [0]

( 6 g + 5 ) 2

Step 1 of 3

Does the trinomial fit the perfect square trinomials pattern, a 2 + 2 a b + b 2 ?

• Is the first term a perfect square? Write it as a square, a 2 .
Is 36 g 2 a perfect square?
Yes — write it as ( 6 g ) 2 .

36 g 2 + 60 g + 25 ( 6 g ) 2

• Is the last term a perfect square? Write it as a square, b 2 .
Is 25 a perfect square?
Yes — write it as 5 2 .

36 g 2 + 60 g + 25 ( 6 g ) 2 ( 5 ) 2

• Check the middle term. Is it 2 a b ?
Is 60 g twice the product of 6 g and 5 ?

36 g 2 + 60 g + 25 ( 6 g ) 2 ( 5 ) 2 2 · ( 6 g ) · 5 60 g

Does it match?
Yes, so we have a perfect square trinomial!

Step 2 of 3

Write it as the square of a binomial.

36 g 2 + 60 g + 25

a 2 + 2 · a · b + b 2 ( 6 g ) 2 + 2 · ( 6 g ) · 5 + 5 2

( a + b ) 2 ( 6 g + 5 ) 2

( a + b ) 2 ( 6 g + 5 ) 2

Step 3 of 3

Check.

( 6 g + 5 ) 2

( 6 g ) 2 + 2 · 6 g · 5 + 5 2

36 g 2 + 60 g + 25