已知4M+N=9,2M-3N=1,求(M+2N)²-(3M-N)²的值

问题描述:

已知4M+N=9,2M-3N=1,求(M+2N)²-(3M-N)²的值

因为4M+N=9,2M-3N=1
所以两式相减得:2M+4N=8 ,M+2N=4,
两式相加得:6M-2N=10 ,3M-N=5
所以(M+2N)²-(3M-N)²=4²-5²=(4+5)*(4-5)=-9