若x^2-y^2=55,x-y=5,求(x+y)^2的值.若（a+b）^2=7,(a-b）^2=4,求ab的值

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若x^2-y^2=55,x-y=5,求(x+y)^2的值.若（a+b）^2=7,(a-b）^2=4,求ab的值
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若x^2-y^2=55,x-y=5,求(x+y)^2的值.若（a+b）^2=7,(a-b）^2=4,求ab的值
若x^2-y^2=55,x-y=5,求(x+y)^2的值.
若（a+b）^2=7,(a-b）^2=4,求ab的值

若x^2-y^2=55,x-y=5,求(x+y)^2的值.若（a+b）^2=7,(a-b）^2=4,求ab的值
∵x²-y²=(x+y)(x-y)=55,x-y=5
∴x+y=(x²-y²)÷(x-y)
=55÷5
=11
∴(x+y)²=11²=121
∵(a+b)²=a²+2ab+b²=7,(a-b)²=a²-2ab+b²=4
∴ab=[(a+b)²-(a-b)²]/4
=(7-4)/4
=3/4

x^2-y^2=55,
（x+y）(x-y)=55
5(x+y)=55
x+y=11
(x+y)²=11²=121
（a+b）^2-(a-b）^2=7-4
a²+2ab+b²-a²+2ab-b²=3
4ab=3
ab=0.75
请好评
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x^2-y^2=55,
（x+y）(x-y)=55
5(x+y)=55
x+y=11
(x+y)²=11²=121
（a+b）^2-(a-b）^2=7-4
a²+2ab+b²-a²+2ab-b²=3
4ab=3
ab=0.75
请好评
~在右上角点击【评价】，然后就可以选择【满意，问题已经完美解决】了。
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