更新1:
The equation should be x square plus 7x and plus 1 equal to 0. I want to find x. Thanks!!
X2+7x+1=0 how do I resolve x in the equation?
回答 (6)
2009-05-06 4:12 pm
✔ 最佳答案
x^2+7x+1=0we can use either quadratic formula or completing the square
I'll use completing the square.
x^2+7x=-1
x^2+7x+49/4=-1+49/4
(x+7/2)^2=45/4
x+7/2=±√(45/4)
x=-7/2±√(9*5)/2
x=-7/2±3√(5)/2
.....-7+3√(5)......-7-3√(5)
x=-----------------,----------------- answer//
...........2.................2
2009-05-06 4:08 pm
x^2 + 7x + 1 = 0
x^2 + 7x = -1
x^2 + 7/2(x) + 7/2(x) = -1
x^2 + 7x/2 + 7x/2 = -1
x^2 + 7x/2 + 7x/2 + 49/4 = -1
(x^2 + 7x/2) + (7x/2 + 49/4) = -1
x(x + 7/2) + 7/2(x + 7/2) = -1
(x + 7/2)(x + 7/2) = -1
(x + 7/2)^2 = -1
x + 7/2 = 屉(-1)
x + 7/2 = ±i (imaginary number)
x = -7/2 ±i
x^2 + 7x = -1
x^2 + 7/2(x) + 7/2(x) = -1
x^2 + 7x/2 + 7x/2 = -1
x^2 + 7x/2 + 7x/2 + 49/4 = -1
(x^2 + 7x/2) + (7x/2 + 49/4) = -1
x(x + 7/2) + 7/2(x + 7/2) = -1
(x + 7/2)(x + 7/2) = -1
(x + 7/2)^2 = -1
x + 7/2 = 屉(-1)
x + 7/2 = ±i (imaginary number)
x = -7/2 ±i
2009-05-06 3:58 pm
x^2 + 7x + 1 = 0
[x + (7/2)]^2 - (7/2)^2 + 1 = 0
[x + (7/2)]^2 - 12.25 + 1 = 0
(x + 3.5)^2 - 11.25 = 0
(x + 3.5)^2 = 11.25
x + 3.5 = +/- sqrt 11.25
x + 3.5 = +/- 3.3541
x = +/- 3.3541 - 3.5
x = 3.3541 - 3.5
x = -0.1459
...OR...
x = -3.3541 - 3.5
x = -6.8541
[x + (7/2)]^2 - (7/2)^2 + 1 = 0
[x + (7/2)]^2 - 12.25 + 1 = 0
(x + 3.5)^2 - 11.25 = 0
(x + 3.5)^2 = 11.25
x + 3.5 = +/- sqrt 11.25
x + 3.5 = +/- 3.3541
x = +/- 3.3541 - 3.5
x = 3.3541 - 3.5
x = -0.1459
...OR...
x = -3.3541 - 3.5
x = -6.8541
2009-05-06 3:52 pm
You need the quadratic formula
(-b +- SQRT(b²-4*a*c))/(2*a)=x
so (-7+- SQRT(49-4))/ 2
=( -7-3*SQRT(5)) /2 or ( -7+3*SQRT(5)) /2
(-b +- SQRT(b²-4*a*c))/(2*a)=x
so (-7+- SQRT(49-4))/ 2
=( -7-3*SQRT(5)) /2 or ( -7+3*SQRT(5)) /2
2009-05-06 3:50 pm
x^2+7x+1=0
quadratic formula
a=1 b=7 c=1
-7+/- sq rt 7^2-4(1)(1)/2
-7+/- sq rt 49-4/2
-7+/- sq rt 45/2
-7 +/- 3 sq rt 5 / 2=x
quadratic formula
a=1 b=7 c=1
-7+/- sq rt 7^2-4(1)(1)/2
-7+/- sq rt 49-4/2
-7+/- sq rt 45/2
-7 +/- 3 sq rt 5 / 2=x
2009-05-06 3:50 pm
use the quadratic equation
x = (-b +-sqrt(b^2 - 4ac))/2a
a = 1
b = 7
c = 1
substitute these values in the equation and you will get two values, these are your answers.
x = (-b +-sqrt(b^2 - 4ac))/2a
a = 1
b = 7
c = 1
substitute these values in the equation and you will get two values, these are your answers.
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