（1）（-2x²y³)².(xy) · (xy)³

(1)(-2x²y³)².(xy) • (xy)³ =4x^8 y^10
(2)(2a+3b)(2a-b)=4a²-2ab+6ab-3b²=4a²+4ab-3b²
(3)5x²(x+1)(x-1)=5x²(x²-1)=5x^4 -5x²
(4)(2x+y-1)² =(2x+y) ²-2(2x+y)+1= 4x²+4xy+y²-4x-2y+1
(5)59.8×60.2=(60-0.2)*(60+0.2)=60²-0.2²=3600-0.04= 3599.96
(6)198²=(200-2) ²=200²-2*2*200+2²=40000-800+4=39204
(7)(2a) ²•b^4=4a² b^4
(8) (-2/3 a^7b^5)÷3/2a² b^5= (-2* a^7 b^5* 2a² b^5)/ (3*3) -----a七b五 不为分母吧
= -4/9( a^9 b^10)
=(-2 * 2a² b^5)/ (3 a^7 b^5*3) = -4/(9 a^5)------- a七b五 为分母
(9)（6/5 a³ x^4-0.9ax³）÷3/5ax³=2a²x - 1.5
(10)（7x²y³ -8x³ y²z）÷8x²y²=(7/8) y - xz
(11)12^13÷(3^10•4^11)=(3*4)^13÷(3^10•4^11)=3³•4²=27•16=432
(12)(因式分解题)
1. 25x²-16y²=(5x) ²- (4y) ²= (5x-4y)(5x+4y) -----平方差
2.(a-b)(x-y)-(b-a)(x+y)=(a-b)[(x-y)+(x+y)]=2x(a-b)
3.a²-4ab+4b²=a²- 2•a•2b+(2b) ²=(a-2b) ²
4. 4+12(x-y)+9(x-y)²=2² + 2*2*3(x-y) +9(x-y)²=[2+3(x-y)]²=(3x-3y+2) ²
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