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AlgebraB-2

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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 105-foot 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

  • AlgebraB-2 - ,

    since (x+a)^2 = x^2+2a+a^2, you need 2a=12, and n=a^2

    x^2+4x-96=0
    what factors of 96 are 4 apart?
    (x-12)(x+8) = 0

    x^2+14x+130=0
    the discriminant is 196-420 < 0

    set h=0 and solve for t
    –16t^2 + 156t + 105 = 0

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