3x mũ 2 +4.(x-1).(x+1)-7x.(x-1)=x+12
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BT
0
25 tháng 9 2021
x^3 + 3x^2 + 3x +1 = ( x +3 ) ^3 - 27z^3 = ( x+3-27 ).[(x+3)^2 - 27 (x +3) + 27^2 ]
DQ
6
25 tháng 9 2021
=20000000000000000000000000000000000000000000000000000000000000000000000000+999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
Đúng chưa lại bảo sai đi
\(3x^2+4\left(x-1\right)\left(x+1\right)-7x\left(x-1\right)=x+12\)
\(\Rightarrow3x^2+4\left(x^2-1^2\right)-7x^2+7x=x+12\)
\(\Rightarrow3x^2+4x^2-4-7x^2+7x-x-12=0\)
\(\Rightarrow\left(3x^2+4x^2-7x^2\right)+\left(7x-x\right)+\left(-12-4\right)=0\)
\(\Rightarrow6x-16=0\)
\(\Rightarrow6x=16\)
\(\Rightarrow x=\frac{8}{3}\)