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What value is needed to fill in the blank to make this a perfect square trinomial 4x2 + __x + 81?
To find the middle term, we want to use the generic quadratic equation as template
a2 + 2ab
+ b2
4x2 + ____x + 81
to find the value of a and b, we want to take the square root of each
√
4x2
= 2x
√
81
= 9
2ab = 2(2x)(9)
= 36x
4x2 + 36x + 81
The middle term is 36x