Question 8:
What is the value of c such that: x2 + 14x + c, is a perfect-square trinomial?
a. 7
b. 98
c. 196
d. 49
4 answers
I answered a. 7. Is that correct?
Yes.
( x + c ) ^ 2 = x ^ 2 + 2 * x * c + c ^ 2
In this case :
2 x c = 14 x Divide both sides bny 2 x
2 x c / 2 x = 14 x / 2 x
c = 7
So :
( x + c ) ^ 2 = x ^ 2 + 2 * x * c + c ^ 2
( x + 7 ) ^ 2 = x ^ 2 + 2 x * 7 + 7 ^ 2 =
x ^ 2 + 14 x + 49
( x + c ) ^ 2 = x ^ 2 + 2 * x * c + c ^ 2
In this case :
2 x c = 14 x Divide both sides bny 2 x
2 x c / 2 x = 14 x / 2 x
c = 7
So :
( x + c ) ^ 2 = x ^ 2 + 2 * x * c + c ^ 2
( x + 7 ) ^ 2 = x ^ 2 + 2 x * 7 + 7 ^ 2 =
x ^ 2 + 14 x + 49
so, even though Bosnian started out with a yes his work shows that the answer was D, not A.
The answer is 49
0 answers