.
Bài 4:
\(M+\left(5x^2-2y^3\right)=10x^2+4y^3\)
\(=>M=\left(10x^2+4y^3\right)-\left(5x^2-2y^3\right)\)
\(M=10x^2+4y^3-5x^2+2y^3\)
\(M=\left(10x^2-5x^2\right)+\left(4y^3+2y^3\right)\)
\(M=5x^2+6y^3\)
Vì \(M+N=8x^2-3y^2\)
\(=>N=\left(8x^2-3y^2\right)-\left(5x^2+6y^3\right)\)
\(N=8x^2-3y^2-5x^2-6y^3\)
\(N=\left(8x^2-5x^2\right)-3y^2-6y^3\)
\(=>N=3x^2-3y^2-6y^3\)
Thôi mk tự làm đề lun
M+N=(-6x2+5xy-13y2)+(x2-5xy+2y2)
= -6x2+5xy-13y2+x2-5xy+2y2
= (-6x2+x2)+(5xy-5xy)+(-13y2+2y2)
= -5x2- 9y2
M-N=(-6x2+5xy-13y2)-(x2-5xy+2y2)
= -6x2+5xy-13y2-x2+5xy-2y2
= (-6x2-x2)+(5xy+5xy)+(-13y2-2y2)
= -7x2+10xy-15y2
N-M=(x2-5xy+2y2)-(-6x2+5xy-13y2)
=x2-5xy+2y2+6x2_5xy+13y2
= (x2+6x2)+(-5xy-5xy)+(2y2+13y2)
= 7x2-10xy+15y2
