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问题: 若x+y=8,x^2y^2=4,x^2+y^2=?a^2-4a+b^2-10b+29=0,a=?b=

解答:

(1){x+y=8,x^2y^2=4} ==>x+y=8且xy=土2;故x^2+y^2=(x+y)^2-2xy=64干4,即x^2+y^2=68或60。(2)a^2-4a+b^2-10b+29=0 ==>(a^2-4a+4)+(b^2-10b+25)=0 ==>(a-2)^2+(b-5)^2=0,因(a-2)^2>=0,(b-5)^2>=0故(a-2)^2=0,(b-5)^2=0,故a=2,b=5