只要填空答案.
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只要填空答案.只要填空答案.只要填空答案.13.114.815.-3x²+6x-117.5a^4（a-b)^618.①19.2420.14,4,2/7原式=1.2²×6×10^7-
只要填空答案.
只要填空答案.
只要填空答案.
13.1
14.8
15.-3x²+6x-1
17.5a^4（a-b)^6
18.①
19.24
20.14,4,2/7
原式=1.2²×6×10^7-2×10^7
=(1.44×6-2)×10^7
=6.64×10^7.
(4)
原式=2（2x-3y)(x-y)-[(x/2)²-(3y)²-(x/2)²+xy-(2y)²]
=2(2x²-5xy+3y²)-(xy-13y²)
=4x²-10xy+6y²-xy+13y²
=4x²-11xy+19y².
(5)
原式=[(2x+3y)(2x-3y)]²-[(x+2y)(x-2y)]²
=(4x²-9y²)²-(x²-4y²)²
=16x^4-72x²y²+81y^4-(x^4-8x²y²+16y^4)
=16x^4-72x²y²+81y^4-x^4+8x²y²-16y^4
=15x^4-64x²y²+65y^4