AlgebraB2
posted by Jennifer W. on .
I need help with figuring out how to do these problems to get the right answer. Appreciate any help. Thanks.
Multiple choice:
1. What is the value of n so that the expression x² + 12x + n is a perfect square trinomial?
6
36
72
144
2. What are the solutions of the equation x2 + 4x = 96?
2, –48
–12, 8
–2, 48
12, –8
3. What are the solutions of the equation x2 + 14x = –130?
2, –16
10, –13
–2, 16
no solution
4. A rocket is launched from atop a 105foot cliff with an initial velocity of 156 ft/s. The height of the rocket above the ground at time t is given by h = –16t2 + 156t + 105. When will the rocket hit the ground after it is launched? Round to the nearest tenth of a second.
4.9 s
9.8 s
0.6 s
10.4 s

since (x+a)^2 = x^2+2a+a^2, you need 2a=12, and n=a^2
x^2+4x96=0
what factors of 96 are 4 apart?
(x12)(x+8) = 0
x^2+14x+130=0
the discriminant is 196420 < 0
set h=0 and solve for t
–16t^2 + 156t + 105 = 0