这2题数学怎么做
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8、原式=(a^2-b^2)/ab
=(a+b)(a-b)/ab
=4×2号3/1
=8根号3
9、原式=(x+2y)(x-2y)y/(x+2y)^2乘以(4xy+x^2-2xy)/(x-2y)
=(x+2y)(x-2y)y/(x+2y)^2乘以x(x+2y)/(x-2y)
=xy
=(根号2-1)×(根号2+1)
=2-1
=1
=(a+b)(a-b)/ab
=4×2号3/1
=8根号3
9、原式=(x+2y)(x-2y)y/(x+2y)^2乘以(4xy+x^2-2xy)/(x-2y)
=(x+2y)(x-2y)y/(x+2y)^2乘以x(x+2y)/(x-2y)
=xy
=(根号2-1)×(根号2+1)
=2-1
=1
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