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3x 2y 5x 2

解:3x-y=5 (1) 5x+2y=23 (2) (1)*2+(2) 11x=33 x=3 (3) 将(3)待人(1)并解得 y=4 所以原方程组的解是: x=3 y=4

解:-3x+2y-5x-y =-3x+2y-5x-y =-3x-5x+2y-y =-8x+y

方法一:①×2得:6x-2y=10③,②+③得:11x=33,x=3.把x=3代入①得:9-y=5,y=4.所以 x=3 y=4 .方法二:由①得:y=3x-5③,把③代入②得:5x+2(3x-5)=23,11x=33,x=3.把x=3代入③得:y=4.所以 x=3 y=4 .

求适合方程的实数x和y的值 (3x+2y)+(5x-y)i=17-2i 解:由题意,得 3x+2y=17 5x-y=-2 所以 x=1 y=7

解:原式=3x^2y-3[4xy^2-2(5x^2y-6xy^2)] =3x^2y-12xy^2+30x^2y-36xy^2 =(3+30)x^2y-(12+36)xy^2 =33x^2y-48xy^2

3x+2y=2① 5x-4y=18② ,①×2得,6x+4y=4③,②+③得,11x=22,解得x=2,把x=2代入①得,3×2+2y=2,解得y=-2,∴方程组的解是 x=2 y=-2 .

A、不是同类项不能合并,故选项错误;B、-9y2+6y2=-3y2,故选项错误;C、a2?a3=a5,正确;D、(a3)2=a6,故选项错误.故选C.

解:[(5x-5y)/3x^2y]X[9xy^2/(x^2-y^2)] =[5(x-y)/3x^2y]X[9xy^2/(x+y)(x-y)] =[45xy^2(x-y)]/[3x^2y(x+y)(x-y)] =15y/x(x+y) =15y/(x^2+xy). 知识要点:分式乘法法则 分式乘以分式,分子的积作为积的分子,分母的积作为积的分母 注意点 运算结...

∵(3x+2y-5) 2 与|5x+3y-8|互为相反数,∴(3x+2y-5) 2 +|5x+3y-8|=0,即 3x+2y-5=0① 5x+3y-8=0② ,解得: x=1 y=1 .故答案为:1,1.

(1)若用代入法解,可把②变形,得y=5x-2,代入①,得3x-2(5x-2)=-3;(2)若用加减法解,可把②×2,把两个方程的两边分别相减,得到的一元一次方程是7x=7.故答案为:(1)5x-2;3x-2(5x-2)=-3;(2)相减;7x=7.

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