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(1) (m—n)²—n² (2)49(a-b)²—16(a+b)²

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(1) (m—n)²—n² (2)49(a-b)²—16(a+b)²
(3) (2x+y)²—(x+2y)² (4) (x²+y²)²—x²y²
(5)3ax²—3ay²
(1) (m—n)²—n² (2)49(a-b)²—16(a+b)²
(1) (m—n)²—n²
=(m-n+n)×(m-n-n)
=m×(m-2n)
=m²-2mn
(2)49(a-b)²—16(a+b)²
=[7(a-b)]² - [4(a+b)]²
=(7a-7b+4a+4b)×(7a-7b-4a-4b)
=(11a-3b)×(3a-11b)
=33a²+33b²-130ab
(3) (2x+y)²—(x+2y)²
=(2X+Y+X+2Y)×(2X+Y-X-2Y)
=(3X+3Y)×(X-Y)
=3X²-3Y²
(4) (x²+y²)²—x²y²
=(x²+y²+xy)×(x²+y²-xy)
=X^4+X²Y²+X³Y+X²Y²+Y^4+XY³-X³Y-XY³-X²Y²
=X^4+Y^4+X²Y² ^4表示4次方
(5)3ax²—3ay²
=3a(X²-Y²)
=3a(X+Y)(X-Y)
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