已知x⒉+y⒉=5,xy=-1,求5x⒉-3xy-4y⒉-11xy+(-9x⒉)的值
问题描述:
已知x⒉+y⒉=5,xy=-1,求5x⒉-3xy-4y⒉-11xy+(-9x⒉)的值
答
5x⒉-3xy-4y⒉-11xy+(-9x⒉)
=5x⒉-3xy-4y⒉-11xy-9x⒉
=-4x⒉-3xy-4y⒉-11xy
=-4(x⒉+y⒉)-14xy
=-4*5-14*(-1)
=-20+14
=-6