Solve by factoring:
x2 – 9x = -8
Solve by factoring:?
2008-04-25 5:03 pm
回答 (8)
2008-04-25 5:07 pm
✔ 最佳答案
x2 – 9x = -8x2 – 9x +8 =0
x2 - 8x - x + 8 =0
x(x-8) -1(x-8)=0
(x-1) (x-8) =0
(x-1)=0 or (x-8)=0
x = 8 or 1
2008-04-26 12:19 am
x^2 - 9x = -8
x^2 - 9x + 8 = 0
so (x-8)(x-1) = 0
therefoe x = 8 or x = 1
x^2 - 9x + 8 = 0
so (x-8)(x-1) = 0
therefoe x = 8 or x = 1
2008-04-26 12:16 am
x2-9x= -8
bring the -8 to the LHS
x2-9x+8=0
x2-8x-x+8=0
x(x-8)-1(x-8)=0
(x-1)(x-8)=0
x=1 or x=8
bring the -8 to the LHS
x2-9x+8=0
x2-8x-x+8=0
x(x-8)-1(x-8)=0
(x-1)(x-8)=0
x=1 or x=8
2008-04-26 12:13 am
So, you want to set the whole thing to 0.
x^2-9x+8=0
You kind of just try the different factors for 8:
Either 1 and 8 or 2 and 4.
1 and 8 seem more likely to get 9.
Its -9, though, so it's possible that -1+-8 or -1-8=9
and that (-1)*(-8)=+8 (since the negatives cancel out).
So, now we have (x-1)(x-8)=0
Set each factor to zero, so x-1=0, x=1
and x-8=0, x=8.
x can be 1 or 8.
Note: this problem is easier to understand when you check by foiling (x-1)(x-8) to get x^2-9x+8.
Hope all this helps!
x^2-9x+8=0
You kind of just try the different factors for 8:
Either 1 and 8 or 2 and 4.
1 and 8 seem more likely to get 9.
Its -9, though, so it's possible that -1+-8 or -1-8=9
and that (-1)*(-8)=+8 (since the negatives cancel out).
So, now we have (x-1)(x-8)=0
Set each factor to zero, so x-1=0, x=1
and x-8=0, x=8.
x can be 1 or 8.
Note: this problem is easier to understand when you check by foiling (x-1)(x-8) to get x^2-9x+8.
Hope all this helps!
2008-04-26 12:09 am
x² â 9x = -8 â x² â 9x + 8 = 0
x² â 9x + 8 = (x â 1)(x â 8) = 0 â (x â 1) = 0 or (x â 8) = 0, so x = 1 or 8
x² â 9x + 8 = (x â 1)(x â 8) = 0 â (x â 1) = 0 or (x â 8) = 0, so x = 1 or 8
2008-04-26 12:08 am
x^2 - 9x = -8
x^2 - 9x + 8 = 0
(x - 8)(x - 1) = 0
x - 8 = 0
x = 8
x - 1 = 0
x = 1
â´ x = 8 , 1
x^2 - 9x + 8 = 0
(x - 8)(x - 1) = 0
x - 8 = 0
x = 8
x - 1 = 0
x = 1
â´ x = 8 , 1
2008-04-26 12:07 am
(x-8)(x-1)
2008-04-26 12:07 am
x² - 9x + 8 = 0
(x - 8)(x - 1) = 0
x = 1, 8
(x - 8)(x - 1) = 0
x = 1, 8
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