x^2 - 7x - 8=0
A=1
B=-7
C=-8
D= B^2-4*A*C = 81
sqrt(D)=9
Formula:
x = (-B+/-sqrt(D))/(2*A)
x1 = (7+9)/2 =8
x2 = (7-9)/2 = -1
Roots are 8 and -1
2006-12-17 01:10:49
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answer #1
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answered by Som™ 6
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rearrange the terms so that the whole system is summed to zero:
x^2 - 7x + 8 = 0
now, note the coefficients on each term, and label them from the greatest order to the least (careful with signs):
a = 1 (from 1 * x^2)
b = -7 (from -7 * x^1)
c = 8 (from 8 * x^0)
now, solve the quadratic formula for the two roots
root1 = ( -b + sqrt(b^2 - 4ac) ) / 2a
root2 = ( -b - sqrt(b^2 - 4ac) ) / 2a
in some cases you will get imaginary numbers, but that is usually ok. if the terms inside the sqrt are negative, then you will get an imaginary (complex) number
2006-12-17 01:22:40
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answer #2
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answered by otis_hobson 3
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to make a quadratic equation
x^2 -7x -8 = 0 an obvious solution is x= -1
as the produncts of root = -8 the other root is 8
I GIVE YOU THE QUADRATIC FORMULA
x1 =( 7 + ( 49+4*8)^0.5)/2 = 8
x2 =( 7 - ( 49+4*8)^0.5)/2 = -1
2006-12-17 01:32:29
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answer #3
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answered by maussy 7
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(x-8)(x+1)
X=8 or X=-1
2006-12-17 03:31:43
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answer #4
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answered by sweetgirl5900 2
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x² = 7x + 8
x² - 7x - 8 = 0
- - - - - - - - -
Quadratic formula
x = - b ± √b² - 4ac/2a
x = -(-7) ± √( - 7)² - 4(1)(- 8) / 2(1)
x = 7 ± √49 - (- 32) / 2
X = 7 ± √49 + 32 / 2
X = 7 ± √81/ 2
X = 7 / 2 ± 9 / 2
X = 3.5 ± 4.5
- - - - - - - --
Solving for +
x = 3.5 + 4.5
x = 8
- - - - - - - - -
Solving for -
x = 3.5 - 4.5
x = - 1
- - - - - - - -s-
2006-12-17 03:50:58
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answer #5
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answered by SAMUEL D 7
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x^2=7x+8
x^2-7x-8=0
using the quadratic formula ,ax^2+bx+c=0
x= (-b+(b^2-4ac)^0.5)/ 2a or x= (-b-(b^2-4ac)^0.5)/ 2a
thus, you will get your answer as
x=8 or x=1
Now, try solving the similar questions on your own to get the idea.
2006-12-17 01:27:16
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answer #6
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answered by D. Xavier 1
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x^2 - 7x - 8 = 0
delta = 7^2 + 8 * 4 = 81
x1 = (7 + sqrt(delta))/2 = 8
x2 = (7 - sqrt(delta))/2 = -1
2006-12-17 01:11:13
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answer #7
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answered by James Chan 4
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u don't have to it comes out
(x-1)(x+8)
x^2-1x+8x-8, which ends up as x^s-7x-8, same as x^2=7x+8.
2006-12-17 01:11:59
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answer #8
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answered by marajader2d2 3
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one solution is -1 and the other solution is 8.
2006-12-17 04:16:23
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answer #9
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answered by wheels 2
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a=7 b=5 c=8 so: -5 +/- (squared roots of) 25-4(7)(8) ____________________________ all divided with the help of two -5 +/- (squared roots of) 25-224 __________________________ all divided with the help of two -5 +/- (squared roots of) -199 -5 +/- i (squared roots of) 199 X= -5 + i (squared roots of) 199 ________________________ all divided with the help of two x= -5 - i (squared roots of) 199 ________________________ all divided with the help of two
2016-11-30 21:15:05
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answer #10
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answered by picart 4
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