x² 4xy 4y² 4y-3-搜答案-大师作文网

解题思路：用x2的取值范围、二次函数的的性质、均值不等式，换元法求函数的值域解题过程：

原式=-(x-y)³(x-y-1)

写清楚点点比如说前面是X/X还是X/(X-Y)打上括号分段这样才能清楚的做

3(x+y)+3(y-x)=1(1)3(x+y)+4(y-x)=-1(2)(2)-(1)得y-x=-2(3)代入（1）3（x+y)-6=1x+y=7/3=>x=7/3－y又由（3）得x=y+2y+2=

由(1)得3x+3y+2x-2y=365x+y=36(3)由(2)得4x+4y-3x+3y=-20x+7y=-20(4)(3)×7-(4)得34x=272∴x=8把x=8代入(3)得y=-4∴x=8y

{(x+y)/2+(x-y)/3=63(x+y)+2(x-y)=36(1)4(x+y)-3(x-y)=-20(2)由（1）*3+(2)*2得9(x+y)+6(x-y)+8(x+y)-6(x-y)=36

(x-3y)(y+2x)-(4y-3x)(3x+4y)=2x^2-3y^2-5xy+9x^2-16y^2=11x^2-5xy-19y^2

(2x+y)(2x-3y)+x(2y+y)=(2y+y)(2x-3y+x)=(2y+y)(3x-3y)=3(2y+y)(x-y)2a(x-y)-4b(x-y)=2(x-y)(a-2b)

解题思路：根据题意，由根式和绝对值的知识可求解题过程：varSWOC={};SWOC.tip=false;try{SWOCX2.OpenFile("http://dayi.prcedu.com/inc

（x+2)(x+3)=x²+5x+6(x-4)(x+1)=x²-3x-4(y+4)(y-2)=y²+2y-8(y-5)(y-3)=y²-8y+15x²

啊

=25x²-9y²+9x²-24xy+16y²=34x²-24xy+7y²

解题思路：对于这种等式一定可以化成平方相加的形式，这里面要使用到完全平方公式。解题过程：

(2x-y)(2x+y)-2(3x-4y)(4y+3x)=4x²-y²-2(9x²-16y²)=4x²-y²-18x²+32y&s

3(x+y)-4(x-y)=4(x+y)/2+(x-y)/6=1令a=x+y,b=x-y3a-4b=4(1)a/2+b/6=1则3a+b=6(2)(2)-(1)5b=2b=2/5a=(6-b)/3=2

（5x+3y)(3y-5x)-(4x-y)(4y+x)=(3y)^2-(5x)^2-(4x^2+15xy-4y^2)=9y^2-25x^2-4x^2-15xy+4y^2=13y^2-15xy-29x^

(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

用提取公因式法,提取（x+3y)原式=（x+3y)[(3x-4y)-(x-2y)]=(x+3y)(2x-2y)=2(x+3y)(x-y)

(x+3y-4)(2x-y)

原式等于2x^2-xy+6xy-3y^2-8x+4y=2x^2+5xy-3y^2-8x+4y