问题补充:
已知实数a,b,x,y满足ax+by=3,ay-bx=5,则(a2+b2)(x2+y2)的值是________.
答案:
34
解析分析:将ax+by=3,ay-bx=5这两式两边平方后相加,最经过提取公因式,左边可得(a2+b2)(x2+y2)至此问题解决.
解答:由题意得,ax+by=3???? ①ay-bx=5?????②①2得a2x2+b2y2+2abxy=9?????? ③②2得a2y2+b2x2-2abxy=25????? ④③+④得a2x2+b2y2+a2y2+b2x2=34a2(x2+y2)+b2(x2+y2)=34(a2+b2)(x2+y2)=34故