Question

初二下册数学题三道~

1.化简:2x²y/3mn²·5m²n/4xy²÷5xym/3n
2.化简:x²/y·y/x÷（-y/x）
3.化简：（xy-x²）·xy/x-y

要过程!!!!

Answer 1

1.化简:2x²y/3mn²· 5m²n/4xy² ÷5xym/3n
=（2x²y*5m²n*3n）/（3mn²· 4xy² *5xym）【为了简算，把所有的分子、分母分开，不易出错】
=1/(2y²)
2.化简:x²/y·y/x÷（-y/x）
=-x*x/y
=-x^2/y
3.化简：（xy-x²）·xy/x-y
=x(y-x)*xy/(x-y)
=-x^2y

Answer 2

2x²y/3mn²·5m²n/4xy²÷5xym/3n
=2x²y/3mn²·5m²n/4xy²·3n/5xym
=1/2y²
x²/y·y/x÷（-y/x）
=x²/y·y/x·x/-y
=-y
（xy-x²）·xy/x-y
=-x(x-y)·xy/x-y
=-x²y

Answer 3

2x²y/3mn²·5m²n/4xy²÷5xym/3n=5xm/6yn·3n/5xym=1/2y^2
x²/y·y/x÷（-y/x）=x·(-x/y)=-x^2/y
(xy-x²）·xy/x-y=-x(x-y)·xy/(x-y)=-x^2y