Question

what value of c makes 36x^2+84x+c a perfect square trinomial?
a) 49
b) 7
c) 9
d) 4

Answer 1

(6x+7) (6××7)
Multiply 6x by 6x 36×2
6×(7) =42×
7 (6×)=42×
7 [7)=49

Answer 2

36x^2 + 84x + c
The middle term in a perfect square trinomial =
2* sqrt a * sqrt c
Divide 84 by 2 = 42
Take the sqrt of 36 = 6
42/6 = 7
sqrt c = 7
So c = 49