6ab/5c²·10c/3b=?-7x/3yz·（-9y²、x²）=?

6ab/5c²*10c/3b
=60abc/(15bc²)
=4a/c
-7x/3yz*(-9y²*x²)
=21x^3y²/(yz)
=21x^3y/z2m/5n÷4m²/10n³=？-x/5y÷(-4x²/5y²)=？4a+4b/5ab·15a²b/a²-b²=？x²-4y²/x²+4x+4·x+2/3x²+6xy=?2m/5n÷4m²/10n³=2m/5n*10n^3/4m²=n²/m-x/5y÷(-4x²/5y²)=x/5y*5y²/4x²=y/4x4a+4b/5ab·15a²b/a²-b²=4(a+b)/5ab*15a²b/[(a+b)(a-b)]=12/(a-b)x²-4y²/x²+4x+4·x+2/3x²+6xy=(x+2y)(x-2y)/(x+2)²*(x+2)/[3x(x+2y)]=(x-2y)/(x+2)