Question

what value in place of the question mark makes the polynomial below a perfect square trinomial? 9x2+?x+49

Answer 1

the missing number should be the square root of the last number times 2 for a perfect trinomial

 so square root of 49 = 7

7*2 =14

 so the missing number should be 14

 

Answer 2

U take the sqrt of the first term, which happens to be 3x...then u take the square root of the 3rd term, which is 7, then u multiply that product by 2....
3x * 7 = 21x.....21x * 2 = 42x

lets check..
9x^2 + 42x + 49 = (3x + 7)^2...correct

so ur middle term will be 42x