1/ a/ Thu gọn:
\(A=x^2+5x+4x^2-7+2x-\dfrac{9}{2}\)
\(=\left(x^2+4x^2\right)+\left(5x+2x\right)+\left(-7-\dfrac{9}{2}\right)\)
\(=5x^2+7x-11,5\)
\(B=2x^2+8-4x+3+5x\)
\(=2x^2+\left(5x-4x\right)+\left(8+3\right)\)
\(=2x^2+x+11\)
\(C=4x+3-5x^2+7\)
\(=-5x^2+4x+\left(3+7\right)=-5x^2+4x+10\)
b/ (mk lm 3 phép cơ bản nhé)
\(A+B=\left(5x^2+7x-11,5\right)+\left(2x^2+x+11\right)\)
\(=\left(5x^2+2x^2\right)+\left(7x+x\right)+\left(11-11,5\right)\)
\(=7x^2+8x-0,5\)
\(A-B=\left(5x^2+7x-11,5\right)-\left(2x^2+x+11\right)\)
\(=5x^2+7x-11,5-2x^2-x-11\)
\(=\left(5x^2-2x^2\right)+\left(7x-x\right)+\left(-11,5-11\right)\)
\(=3x^2+6x-22,5\)
\(A+B+C=\left(5x^2+7x-11,5\right)+\left(2x^2+x+11\right)+\left(-5x^2+4x+10\right)\)
\(=\left(5x^2+2x^2-5x^2\right)+\left(7x+x+4x\right)+\left(11+10-11,5\right)\)
\(=2x^2+12x+9,5\)
