Question

若y分之x等于3分之4,求2x²+3xy-5y²分之3x²-5xy+2y²的值

若y/x等于3/4,求2x²+3xy-5y²/3x²-5xy+2y²的值

Answer 1

y分之x等于3分之4--------------------------这题分母是y,分子是x

2x²+3xy-5y²分之3x²-5xy+2y²-----------2x²+3xy-5y²是分母,3x²-5xy+2y² 是分子
=(x-y)(2x+5y)分之(x-y)(3x-2y)
=(2x+5y)分之(3x-2y)
=(2x/y+5)分之(3x/y-2)
=(2×4/3+5)分之(3×4/3-2)
=6/23

y/x=3/4-------------------------这题分母是x,分子是y,x分之y等于4分之3
(2x²+3xy-5y²)/(3x²-5xy+2y²)-------------------2x²+3xy-5y²是分子,3x²-5xy+2y² 是分母
=(x-y)(2x+5y)/(x-y)(3x-2y)
=(2x+5y)/(3x-2y)
=(2+5y/x)/(3-2y/x)
=(2+5×3/4)/(3-2×3/4)
=23/6

这里是两个不同的题目哦,你看下分子分母是哪个哦

Answer 2

2x²+3xy-5y²/3x²-5xy+2y²
=[2+3(y/x)-5(y/x)²]/[3-5(y/x)+2(y/x)²]
=(2+9/4-45/16)/(3-15/4+9/8)
=(32+36-45)/(48-60+18)
=23/6