x² 3xy 2y²-7x-13y 6

1.(x+1)(x+3)(x+5)(x+7)+15=[(x+1)(x+7)][(x+3)(x+5)]+15=(x^2+8x+7)(x^2+8x+15)+15=(x^2+8x+7)[(x^2+8x+7)

-x^y^7+y^8)(这里有问题,x的几次方?再问：就是一次方再答：(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-xy^7+y^8)(x^2+xy+y^2)=（x^8-x^7y+x^

(3x+y)(3x-y)=9x²-3xy+3xy-y²=9x²-y²

2(y-x)²-7(x-y)+6(x-y)-3(y-x)²=-(y-x)²-(x-y)=-(x-y)²-(x-y)=-(x-y)[(x-y)+1]=(y-x)(

∵x+7y=y-3x∴x＝−32y∴x2−y2x2+y2=94x2− y294x2+y2=513故答案为513

3(X-Y)²-4(X-Y)+7(X-Y)-6(X-Y)²=(3-6)(X-Y)²+(-4+7)(X-Y)=-3(X-Y)²+3(X-Y)

2x+y+z=10(1)x+2y+z=-6(2)x+y+z=8(3)(2)-(3):y=-14(4)(1)-(2):x-y=16(5)把（4）代入（5）：x+14=16x=2(6)把（4）和（6）代入

(x-y)^8

解题思路：：∵x+y=0,x+13y=1，解得x=1/12,y=-1/12∴x²+12xy+13y²=1/144-1/12+13/144=14/144-1/12=2/144=1/72解题过程：已知x+

7x+[-3x-3（x-2y）]-[5x-（2x-y）]=7X+[-3X-3X+6Y]-[5X-2X+Y]=7X-3X-3X+6Y-5X+2X-Y=5Y-2X

若(x-y)/(x+y)=3那么x-y=3(x+y)x-y=3x+3y故x=-2y所以(x+2y)/(6x-7y)=(-2y+2y)/(6*(-2y)-7y)=0如果不懂,请Hi我,祝学习愉快!

=3x/(x-4y)-(x+y)/(x-4y)-7y/(x-4y)=(3x-x-y-7y)/(x-4y)=(2x-8y)/(x-4y)=2(x-4y)/(x-4y)=2

(-3x+7y)(-7y-3x)-(x-3y)(2x+3y)=(3x-7y)(3x+7y)+(3y-x)(3y+2x)后半部分相当于(x+a)(x+b)=x^2+(a+b)x+ab=9x^2-49y^

(x-y)(3x-7y)²-4(x-y)(x+y)²=(x-y)[(3x-7y)²-4(x+y)²]=(x-y)(3x-7y-2x-2y)(3x-7y+2x+2

1、(-7x^y)(2x^y-3xy^3+xy)=-14x^(2y)+21x^(y+1)y^3-7x^(y+1)y;2、((x-y)^6)/((y-x)^3)/(x-y)=-(x-y)^3/(x-y)

#includesintjiesheng(intn)//用于计算阶乘如：3!{if(n=1)rerunn;returnn*hh(n-1)}doubledigui(intn,intx)//用以计算y=x

(3x-4y)(5x-4y)-(7x-8y)(6y-5x)=15x²-12xy-20xy+16y²-（42xy-35x²-48y²+40xy）=15x²

x-4y分之3x+4y-x分之x+y-x-4y分之7y=3x/(x-4y)-(x+y)/(x-4y)-7y/(x-4y)=(3x-x-y-7y)/(x-4y)=(2x-8y)/(x-4y)=2

(x-y)^7÷(y-x)^6+(-x-y)^3÷(x+y)^2=(x-y)^7÷(x-y)^6+[-(x+y)^3]÷(x+y)^2=(x-y)+[-(x+y)]=x-y-x-y=-2y