\(A=x^8+64\)
\(A=\left(x^4\right)^2+2.x^4.8+8^2-2.x^4.8\)
\(A=\left(x^4+8\right)^2-16x^4\)
\(A=\left(x^4+8\right)^2-\left(4x^2\right)^2\)
\(A=\left(x^4+8-4x^2\right)\left(x^4+8+4x^2\right)\)
\(B=x^2-3x+xy-3y\)
\(B=\left(x^2+xy\right)-\left(3x+3y\right)\)
\(B=x\left(x+y\right)-3\left(x+y\right)\)
\(B=\left(x+y\right)\left(x-3\right)\)
\(C=\left(x^2+x+1\right)\left(x^2+x+2\right)-6\)
Đặt x2 + x + 1 = a, ta được
\(C=a\left(a+1\right)-6\)
\(C=a^2+a-6\)
\(C=a^2-2a+3a-6\)
\(C=a\left(a-2\right)+3\left(a-2\right)\)
\(C=\left(a-2\right)\left(a+3\right)\)
\(C=\left(x^2+x+1-2\right)\left(x^2+x+1+3\right)\)
\(C=\left(x^2+x-1\right)\left(x^2+x+4\right)\)
