问题
解答题
(1)已知2x-y=
(2)已知(a+b)2=17,(a-b)2=13,求a2+b2与ab的值. |
答案
(1)∵2x-y=
,xy=2,1 64
∴2x4y3-x3y4=x3y3(2x-y)=(xy)3(2x-y)=23×
=1 64
;1 8
(2)∵(a+b)2=17,(a-b)2=13,
∴a2+2ab+b2=17①,a2-2ab+b2=13②,
①+②得:2(a2+b2)=30,a2+b2=15;
①-②得:4ab=4,即ab=1.