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a: \(\left(x+2\right)^2+\left(x+8\right)\left(x+2\right)=0\)
=>(x+2)(x+2+x+8)=0
=>(x+2)(2x+10)=0
=>(x+2)(x+5)=0
=>\(\left[\begin{array}{l}x+2=0\\ x+5=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=-2\\ x=-5\end{array}\right.\)
b: \(B=\left(x+y\right)\left(x^2-xy+y^2\right)-y^3\)
\(=x^3+y^3-y^3=x^3\)
Khi x=10 thì \(B=10^3=1000\)
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a) \(P=x\left(x-y\right)+y\left(x-y\right)=\left(x-y\right)\left(x+y\right)=x^2-y^2=5^2-4^2=9\)
b) \(Q=x\left(x^2-y\right)-x^2\left(x+y\right)+y\left(x^2-x\right)=x^3-xy-x^3-x^2y+x^2y-xy=0\)
a: \(=\left(x-y\right)\left(x+y\right)\)
\(=74\cdot100=7400\)
c: \(=\left(x+2\right)^3\)
\(=10^3=1000\)
a) \(=\left(x-y\right)\left(x+y\right)\)
Thay \(x=87;y=13\) ta đc: \(\left(87-13\right)\left(87+13\right)=74\cdot100=7400\)
b)\(=\left(x-y\right)\left(x^2+xy+y^2\right)=x^3-y^3\)
Thay \(x=10;y=-1\) ta đc:
\(10^3-\left(-1\right)^3=1000-1=999\)
c)\(=\left(x+2\right)^3\)
Thay \(x=8\) ta đc: \(\left(8+2\right)^3=10^3=1000\)
d)\(=x^2-8x+16+1=\left(x-4\right)^2+1\)
Thay \(x=104\) ta đc: \(\left(104-4\right)^2+1=100^2+1=10001\)
a: \(2\left(2x+x^2\right)-x^2\left(x+2\right)+\left(x^3-4x+3\right)\)
\(=4x+2x^2-x^3-2x^2+x^3-4x+3\)
=3
=>Đúng
b: \(x\left(x^2+x+1\right)-x^2\left(x+1\right)-x+5\)
\(=x^3+x_{}^2+x-x^3-x^2-x+5\)
=5
=>Đúng
c: \(3x\left(x-2\right)-5x\left(x-1\right)-8\left(x^2-3\right)\)
\(=3x^2-6x-5x_{}^2+5x-8x^3+24\)
=-x+24
=>Sai
d: \(2y\left(y^2+y+1\right)-2y^2\left(y+1\right)-2\left(y+10\right)\)
\(=2y^3+2y^2+2y-2y^3-2y^2-2y-20\)
=-20
=>Đúng
\(A=\left(x-y\right)\left(x^2-xy\right)-x\left(x^2+2y^2\right)\)
\(=x^3-x^2y-x^2y+xy^2-x^3-2xy^2\)
\(=-2x^2y-xy^2\)
\(=-2\cdot2^2\cdot\left(-3\right)-2\cdot\left(-3\right)^2\)
\(=8\cdot3-2\cdot9\)
=6