4(x-y-1)=3(6-y)-2
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[(2x+y)^2+(y+2x)(y-2x)-2y(4x-y)]/4y=(4x^2+4xy+y^2+y^2-4x^2-8xy+2y^2)/4y=(-4xy+4y^2)/4y=-x+y=-1/2+1/3
原式=(9x²+24xy+16y²-4x²+y²-5x²+6xy-y²)÷(-2y)=(30xy+16y²)÷(-2y)=-15x
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=
3(x+y)-4(x-y)=4,①x+y/2+x-y/6=1,则3(x+y)+(x-y)=6②②-①,得5(x-y)=2,解得x-y=2/5③代入②,得x+y=28/15④③+④,得2x=34/15,
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
很多数学符号,还是写出来方便.
{(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
第二个方程是不是写错了2/(x+y)+3/(x-y)=6是这样吗
原方程组变形得:①3﹙x+y﹚-﹙x-y﹚=4②3﹙x+y﹚+﹙x-y﹚=6∴①+②得:③x+y=10/3②-①得:④x-y=1∴③+④得:x=13/6③-④得:y=7/6∴x=13/6,y=7/6.
第一个两边乘128(x-y)-3(x+y)=-128x-8y-3x-3y=-125x-11y=-12(1)第二个6x+6y-8x+4y=16-2x+10y=16x-5y=-8(2)(1)-(2)×55
(7x-2y)(3x-2y-1)-(4x+3y)(9x+6y)=21x^2-14xy-7x-6xy+4y^2+2y-36x^2-24xy-27xy-18y^2=-15x^2-70xy-7x-14y^2
2(x-y)/3-x+y/4=-1(1)6(x+y)-4(2x-y)=16(2)(1)方程两边同乘以12得8(x-y)-3(x+y)=-12合并同类项得5x-11y+12=0(3)(2)合并同类项得1
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
令a=1/(x+y),b=1/(x-y)4a+6b=3(1)9b-a=1(2)(1)+(2)×46b+36b=3+442b=7b=1/6a=9b-1=1/2所以x+y=1/a=2x-y=1/b=6相加
先把第二个式子两边同乘以6,则第二个式子就变为3(x+y)+(x-y)=6{1}第二个式子减第一个式子得(x-y)=2{2}x-y=2/5将上式带入{1}中得x+y=28/15{3}由{2}{3}得x
{4/x+y+6/x-y=3{9/x-y-1/x+y=1令1/(x+y)=a,1/(x-y)=b则原方程组为{4a+6b=3{-a+9b=1解得{a=1/2{:b=1/6所以{x+y=2{x-y=6解
3x+2y/4=2x+y/5可得x=-3y/10x-y+1/6=2x+y/5x=-6y/5+1/6-3y/10=-6y/5+1/6y=5/27x=-1/18
3(x+y)-4(x-y)=43x+3y-4x+4y=4x-7y=-4(1)x+y/2+x-y/6=13x+3y+x-y=62x+y=3(2)(1)+(2)×715x=17所以x=17/15y=3-2
完整设1/(x+y)=a,1/(x-y)=b原方程组可变为4a+6b=39b-a=1a=9b-136b-4+6b=3b=1/6,a=1/2x+y=2x-y=6所以原方程组的解为:x=4,y=-2
(x+y)/2+(x-y)/6=1x/2+x/6+y/2-y/6=12x/3+y/3=12x+y=3(1)3(x+y)-4(x-y)=43x+3y-4x+4y=4-x+7y=4(2)(1)+2*(2)