\(a,(x^3-x+1)(2x+1)+(x-1)(x+2)\)
\(=2x^4-2x^2+2x+x^3-x+1+x^2-x+2x-2\)
\(=2x^4+x^3+(-2x^2+x^2)+(2x-x-x+2x)+(1-2)\)
\(=2x^4+x^3-x^2+2x-1\)
\(b,(2x+a)(2x-3a)-5a(x+3)\)
\(=4x^2+2ax-6ax-3a^2-5ax-15a\)
\(=4x^2+(2ax-6ax-5ax)-3a^2-15a\)
\(=4x^2-9ax-3a^2-15a\)
Chúc bạn học tốt
a, \(\left(x^3-x+1\right)\left(2x+1\right)+\left(x-1\right)\left(x+2\right)\)
\(=2x^4+x^3-2x^2-x+2x+1+x^2+2x-x-2\)
\(=2x^4+x^3-x^2+2x-1\)
b, \(\left(2x+a\right)\left(2x-3a\right)-5a\left(x+3\right)\)
\(=4x^2-6xa+2ax-3a^2-5ax-15a\)
\(=4x^2-9ax-3a^2-15a\)
a,\(\left(x^3-x+1\right)\left(2x+1\right)+\left(x-1\right)\left(x+2\right)\)
\(=2x\left(x^3-x+1\right)+1\left(x^3-x+1\right)+x\left(x+2\right)-1\left(x+2\right)\)
\(=2x^4-2x^2+2x+x^3-x+1+x^2+2x-x-2\)
\(=2x^4+\left(-2x^2+x^2\right)+\left(2x-x+2x-x\right)+x^3+1-2\)
\(=2x^4-x^2+2x+x^3-1\)
b,\(\left(2x+a\right)\left(2x-3a\right)-5a\left(x+3\right)\)
\(=2x\left(2x-3a\right)+a\left(2x-3a\right)-5a\left(x+3\right)\)
\(=4x^2-6ax+2ax-3a^2-5ax-15a\)
\(=4x^2+\left(-6ax+2ax-5ax\right)-3a^2-15a\)
\(=4x^2-9ax-3a^2-15a\)
a) \(\left(x^3-x+1\right)\left(2x+1\right)+\left(x-1\right)\left(x+2\right)\)
\(=x^3\left(2x+1\right)-x\left(2x+1\right)+1\left(2x+1\right)+x\left(x+2\right)-1\left(x+2\right)\)
\(=2x^4+x^3-2x^2-x+2x+1+x^2+2x-x-2\)
\(=2x^4+x^3-x^2+2x-1\)
b) \(\left(2x+a\right)\left(2x-3a\right)-5a\left(x+3\right)\)
\(=2x\left(2x-3a\right)+a\left(2x-3a\right)-5a\left(x+3\right)\)
\(=4x^2-6ax+2ax-3a^2-5ax-15a\)
\(=4x^2-9ax-3a^2-15a\)
