Question

Tìm x, sao cho

a) x + 7x² = 0

b) x ( x + 2 ) - 5x - 10 = 0

c) x³ + x = 0

GIÚP MIK VỚI

Answer 1

`a)x+7x^2=0`

`<=>x(1+7x)=0`

`<=>[(x=0),(x=-1/7):}`

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`b)x(x+2)-5x-10=0`

`<=>x(x+2)-5(x+2)=0`

`<=>(x+2)(x-5)=0`

`<=>[(x=-2),(x=5):}`

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`c)x^3+x=0`

`<=>x(x^2+1)=0`

  Mà `x^2+1 > 0`

 `=>x=0`

Answer 2

`x+7x^2 = 0`

`x.(7x+1)=0`

`=>` `x=0` hoặc `7x+1=0`

`x=0` hoặc `x = -1/7`

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`x.(x+2)-5x-10=0`

`(x+2).(x-5)=0`

`=>` `x+2=0` hoặc `x-5=0`

`=> x = -2` hoặc `x=5`

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`x^3+x=0`

`x.(x^2 +1)=0`

`=> x = 0` hoặc `x^2 +1=0`

`x=0` hoặc `x^2 = -1(VL)`

Vậy `x=0`