write the equation 4 x(x - 20) = - 396?
回答 (7)
2008-07-26 2:52 pm
✔ 最佳答案
4x(x-20)=-3964x^2-80x+396=0
4(x^2-20x-99)=0
4(x-9)(x-11)=0
so the answer is
x1=9
x2=11
good luck
2008-07-27 1:37 am
4x² - 80x + 396 = 0
x² - 20x + 99 = 0
(x - 11)(x - 9) = 0
x = 11 , x = 9
x² - 20x + 99 = 0
(x - 11)(x - 9) = 0
x = 11 , x = 9
2008-07-26 9:53 pm
4x(x - 20) = -396
x(x - 20) = -396/4
x^2 - 20x = -99
x^2 - 20x + 99 = 0
x^2 - 9x - 11x + 99 = 0
(x^2 - 9x) - (11x - 99) = 0
x(x - 9) - 11(x - 9) = 0
(x - 9)(x - 11) = 0
x - 9 = 0
x = 9
x - 11 = 0
x = 11
â´ x = 9 , 11
x(x - 20) = -396/4
x^2 - 20x = -99
x^2 - 20x + 99 = 0
x^2 - 9x - 11x + 99 = 0
(x^2 - 9x) - (11x - 99) = 0
x(x - 9) - 11(x - 9) = 0
(x - 9)(x - 11) = 0
x - 9 = 0
x = 9
x - 11 = 0
x = 11
â´ x = 9 , 11
2008-07-26 9:49 pm
4x(x-20)=-396
4x^2-80x+396=0
4(x^2-20x-99)=0
4(x-9)(x-11)=0
x=9 or 11
4x^2-80x+396=0
4(x^2-20x-99)=0
4(x-9)(x-11)=0
x=9 or 11
2008-07-26 9:43 pm
I'm assuming by "write", you meant to solve it.
First, distribute:
4x^2 - 80x = -396
Then divide by 4 to simplify:
x^2 - 20x = -99
The add 99:
x^2 - 20x + 99 = 0
Now, factor:
(x - 11)(x - 9) = 0
So, x = 11, 9
Check the answers back in the equation, these are the two possible roots.
(You can also use Quadratic Formula or Completing the Square, but if you realize it can be factored, it's easier to solve)
First, distribute:
4x^2 - 80x = -396
Then divide by 4 to simplify:
x^2 - 20x = -99
The add 99:
x^2 - 20x + 99 = 0
Now, factor:
(x - 11)(x - 9) = 0
So, x = 11, 9
Check the answers back in the equation, these are the two possible roots.
(You can also use Quadratic Formula or Completing the Square, but if you realize it can be factored, it's easier to solve)
2008-07-26 9:43 pm
4x^2 - 80x + 396 = 0
but if you meant by '4' is "for":
x^2 - 20x + 396 = 0
but if you meant by '4' is "for":
x^2 - 20x + 396 = 0
2008-07-26 9:41 pm
OK here it is 4 x(x - 20) = - 396
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