Question

Làm tính nhân:

\(a)\frac{x}{{x + y}}.\frac{{2{\rm{x}} + 2y}}{{3{\rm{x}}y}}\)

\(b)\frac{{3{\rm{x}}}}{{4{{\rm{x}}^2} - 1}}.\frac{{ - 2{\rm{x}} + 1}}{{2{{\rm{x}}^2}}}\)

Answer 1

\(a)\frac{x}{{x + y}}.\frac{{2{\rm{x}} + 2y}}{{3{\rm{x}}y}}\)

\(\begin{array}{l} = \frac{{2{{\rm{x}}^2} + 2{\rm{x}}y}}{{3{\rm{x}}y(x + y)}}\\ = \frac{{2{\rm{x}}(x + y)}}{{3{\rm{x}}y(x + y)}} = \frac{{2{\rm{x}}}}{{3{\rm{x}}y}}\end{array}\)

\(b)\frac{{3{\rm{x}}}}{{4{{\rm{x}}^2} - 1}}.\frac{{ - 2{\rm{x}} + 1}}{{2{{\rm{x}}^2}}}\)

\(\begin{array}{l} = \frac{{3{\rm{x}}( - 2{\rm{x}} + 1)}}{{2{{\rm{x}}^2}(4{{\rm{x}}^2} - 1)}}\\ = \frac{{ - 3{\rm{x}}}}{{2{{\rm{x}}^2}(2{\rm{x}} + 1)}}\end{array}\)