www.ylrr.net > 已知x的平方加3xy减4y的平方等于0,且y不等于0,求x加y分之x减y的值

已知x的平方加3xy减4y的平方等于0,且y不等于0,求x加y分之x减y的值

X^2+3xy-4y^2=(x+4y)(x-y)=0x+4y=0或x-y=0;x=-4y或x=y将x值代入算式x-y/x+y :1、(-4y-y)/(-4y+y)=5/32、(y-y)/(y+y)=0.(y不等于0)答案为5/3或0.

0,5/3

已知x的平方加3xy减4y的平方等于0,(y不等于0),试求x-y/x+y即:X^2+3xy-4y^2=(x+4y)(x-y)=0 x+4y=0或x-y=0;得解:x=-4y或x=y将x值代入算式x-y/x+y : 1、(-4y-y)/(-4y+y)=5/3 2、(y-y)/(y+y)=0.(y不等于0)答案为5/3或0.

先用十字相乘法分解得值 再把它代入式子就行了

x^2 + 3xy -4y^2 = 0 ==> (x+4y)(x-y)=0 ==> x= -4y 或 x=y (1) 当 x = -4y 时,(x-y)/(x+y) = -5y /(-3y) = 5/3 (2) 当 x=y 时, (x-y)/(x+y) = 0 /(x+y) = 0

(x+4y)(x-y)=0x=-4y或x=y当x=-4y时(x-y)/(x+y)=(-4y-y)/(-4y+y)=(-5)/(-3)=5/3当x=y时(x-y)/(x+y)=0

因式分解得(x+4y)(x-y)=0因为y不为0所以x+4y=0即x=-4y…带入要求的式子算得为5/3

由x^2+3xy-4y^2=0可得 (x+4y)(x-y)=0, 由于在 “x-y分之x+y”中x-y为分母,故不能为0,知x=y 不成立; 所以 x+4y=0,得 x=-4y; 于是 (x-y)分之(x+y)既 (x+y)/(x-y)=(-4y+y)/(-4y-y)=-3y/(-5y)=3/5.

x^2-3xy-4y^2=0(x-4y)(x y)=0x=4y 或x=-yx:y =4 或-1

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