SOLUTION: I need to solve by completeing the square: ^ :means exponent 7x^2 - 14x -56=0 I moved 56 to the other side: 7x^2-14x=56 Then i did (b/2)^2 and got 49 as a th

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Question 1072205: I need to solve by completeing the square: ^ :means exponent
7x^2 - 14x -56=0
I moved 56 to the other side: 7x^2-14x=56
Then i did (b/2)^2 and got 49 as a third term: 7x^2-14x+49
I tried to find what added could give me -14 and multiplied could give me 343
Did i do this wrong? plz help
Found 3 solutions by Boreal, jorel1380, rothauserc:
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website!
You have to divide by the leading coefficient to make it 1, then you can proceed.
7(x^2-2x)=7(8)
x^2-2x=8, because both sides are multiplied by 7.
(x2-2x+1)=8+1
(x+1)^2=3^2
(x+1)=+/-3
x=-1+/- 3
x=-2, 4

Answer by jorel1380(3719)   (Show Source):
You can put this solution on YOUR website!
7x�-14x-56=0
Divide by 7
x�-2x-8=0
Factor the equation
(x+2)(x-4)=0
Solve for x
x=-2 or 4. ☺☺☺☺

Answer by rothauserc(4718)   (Show Source):
You can put this solution on YOUR website!
for complete the square to work, the coefficient of x^2 term must be 1
:
7x^2 - 14x -56 = 0
:
7x^2 -14x = 56
:
divide both sides of = by 7
:
x^2 -2x = 8
:
add 1 to both sides of =
:
x^2 -2x +1 = 8 + 1
:
(x - 1)^2 = 3^2
:
take square root of both sides of =
:
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there are two cases
:
1) x - 1 = 3
:
x = 4
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2) x - 1 = -3
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x = -2
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check our answers for x, x = 4 and x = -2
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7x^2 - 14x -56 = 0
:
7(4)^2 -14(4) -56 = 0
:
112 -56 -56 = 0
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112 -112 = 0
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0 = 0
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7(-2)^2 -14(-2) -56 = 0
:
28 +28 -56 = 0
:
56 - 56 = 0
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0 = 0
:
our answers check
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