Đ

`(x+2)(x^2 -2x+4) -x(x^2-2)=15`

`<=> x^3 +8 - x^3 + 2x-15=0`

`<=> 2x-7=0`

`<=> 2x=7`

`<=>x=7/2`

__

`(x-4)^2 -(x-2)(x+2)=6`

`<=>x^2 - 8x+16- x^2 +4-6=0`

`<=> -8x+14=0`

`<=> -8x=-14`

`<=>x=14/8= 7/4`

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`x^4 -2x^3 +x^2-2x=0`

`<=>x(x^3-2x^2+x-2)=0`

`<=> x(x^3+x-2x^2-2)=0`

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

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

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x^2+1=0\\x-2=0\end{matrix}\right.\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\end{matrix}\right.\)

mang đt lên à... báo cô đó-))

ngầu qua^^

`1,3/5 +(-1/3)`

`= 9/15 + (-5)/15`

`= 4/15`

`2,-2/13+(-11)/26`

`= -4/26 +(-11)/26`

`= -15/26`

`3,-2+(-5)/8`

`= -16/8 +(-5)/8`

`= -21/8`

`4,13/20-1/5`

`= 13/20 - 4/20`

`= 9/20`

`5, 2/21 - (-1)/28`

`= 2/21 + 1/28`

`=11/84`

`6, -3 1/2 - 2 1/4`

`= -7/2 - 9/4`

`= -14/4 -9/4`

`= -23/4`

Câụ tách ra nhe^^