$(x^2+1).(x-2)+x^2=4$
$⇔x^3-2x^2+x-2+x^2-4=0$
$⇔x^3-x^2+x-6=0$
$⇔x^3-2x^2+x^2-2x+3x-6=0$
$⇔x^2(x-2)+x(x-2)+3(x-2)=0$
$⇔(x^2+x+3)(x-2)=0$
$⇔x^2+x+3=0$ hoặc $x-2=0$
$+,x^2+x+3=0$
$⇔(x+\dfrac{1}{2})^2+\dfrac{11}{4}=0$(vô lý)
$+,x-2=0$
$x=2$
Vậy `S={2}`
Đáp án:
`x=2`.
Giải thích các bước giải:
`(x^2+1)(x-2)+x^2=4`
`<=>(x^2+1)(x-2)+x^2-4=0`
`<=>(x^2+1)(x-2)+(x-2)(x+2)=0`
`<=>(x-2)(x^2+1+x+2)=0`
`<=>(x-2)(x^2+x+3)=0`
Mà `x^2+x+3=(x+1/2)^2+11/4>=11/4>0`
`<=>x-2=0`
`<=>x=2`
Vậy phương trình có nghiệm duy nhất `x=2`.
giải bài toán này giúp mình với
Trong phòng thì nghiệm, người ta điều chế khí oxit sắt từ Fe3O4 bằng cách dùng O2 oxi hóa sắt ở nhiệt độ cao. Để điều chế được 2,32g Fe3O4 cần dùng: a) Bao nhiêu gam sắt ? b) Bao nhiêu lít khí O2 ( ở đktc)
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