已知x²-y²=6,x-y=1,则x+y等于A.2 B.3 C.4 D.6则么算的
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已知x²-y²=6,x-y=1,则x+y等于A.2 B.3 C.4 D.6
则么算的
D.6
x²-y²
=(x+y)(x-y)
=x+y
=6
∴x+y=6
x²-y²=(x+y)(x-y)
6=x+y
选D
x²-y²=(x+y)×(x-y)=6,
∵x-y=1,
∴x+y=6
x2-y2=(x-y)*(x+y)=6,x+y=6
D.....百度神经,回答会被X
D。6
x²-y²=(x+y)(x-y)