x=（y-5）÷2,4x+3y=65 ； x+y=11,x-y=7；3x-2y=9,x+2y=3各位哥哥姐姐们拜托了,帮我用代入消元法解这些方程,最好有步骤,

3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2 4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) [(x+2y)²-（x+y)(3x-y)-5y²]÷(2x),其中x,y满足x²+4x+y²-y+17/4=0已知、x+y=6且xy=4(1)x²+y² (2)（x-y）² (3)x{四次方}+y{四次方}第一题没错 书上就这样写的！ 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 x+2y=3（x+y）+5 3x-4y=4（x+y）-15 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 已知x-2y=2011,求[(3x+2y)(3x-2y)-(x+2y)(5x-2y)]÷4x的值. 已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y) 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 1.（－2a）³·b²÷(8a³b²) 2.－5x（2x²－3x＋4）+4x³+15x3.（x²-2y²）(x+2y)-2xy(x-y)4.（x-y+z）(x-y-z)化简求值 ［（x+y）(x-y)-(x+y)²-2y(x-2y)］÷(-2y),其中x=5,y=2003 (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuaihuajian 先化简,再求值 [2/3x - 2/x+y（x+y/3x -x-y）]*x/x-y,其中5x+3y=0 先化简,再求值：[(x+2y)²-（x+y）（3x-y）-5y²]÷2x,其中x=-2,y=1/2 先化简,再求值：[(x+2y)²-（x+y）（3x-y）-5y²]÷2x,其中x=-2,y=1/2 先化简,再求值:[(x+2y)²-(x+y)(3x-y)-5y²]÷2x,其中x=-4,y=-3.