Question

Tính nhanh:

a, \(\frac{7}{13}\) . \(\frac{7}{15}\)  - \(\frac{5}{12}\) . \(\frac{21}{39}\) + \(\frac{49}{91}\) . \(\frac{8}{15}\)

 

Ai trả lời giúp mk đii~~

Answer 1

7/13.7/15-5/12.21/39+49/91+8/15

=7/13.7/15-5/12.7/13+7/13.8/15

=7/13.(7/15-5/12+8/15)

=7/13.7/12

=49/156

Answer 2

7/13x7/15-5/12x21/39+49/91x8/15

=7/13x7/15-5/12x7/13+7/13x8/15

=7/13x(7/15-5/12+8/15)

=7/13x7/12

=49/156

Answer 3

7/13.7/15-5/12.21/39+49/91.8/15                        =7/13.7/15-5/12.7/13+7/13.8/15                          =7/13(7/15-5/12+8/15)                                            =7/13.7/12                                                                  =49/156

Answer 4

a ) \(\frac{7}{13}\).\(\frac{7}{15}\)-\(\frac{5}{12}\).\(\frac{21}{39}\)+\(\frac{49}{91}\).\(\frac{8}{15}\)

= \(\frac{7}{13}\).(\(\frac{7}{15}\)-\(\frac{5}{12}\)+\(\frac{8}{15}\))

=\(\frac{7}{13}\).\(\frac{7}{12}\)

=\(\frac{49}{156}\)

hok tốt

Answer 5

7/13.7/15-5/12.7/13+7/13.8/15

7/13.(7/15-5/12+8/15)

7/13.7/12

49/156

Answer 6

a ) \(\frac{7}{13}\).\(\frac{7}{15}\)-\(\frac{5}{12}\).\(\frac{21}{39}\)+\(\frac{49}{91}\).\(\frac{8}{15}\)

= \(\frac{7}{13}\).(\(\frac{7}{15}\)-\(\frac{5}{12}\)+\(\frac{8}{15}\))

=\(\frac{7}{13}\).\(\frac{7}{12}\)

=\(\frac{49}{156}\)

hok tốt

Answer 7

\(\frac{7}{13}.\frac{7}{15}-\frac{5}{12}.\frac{21}{39}+\frac{49}{91}.\frac{8}{15}\)

\(=\frac{7}{13}.\frac{7}{15}-\frac{5}{12}.\frac{7}{13}+\frac{7}{13}.\frac{8}{15}\)

\(=\frac{7}{13}.\left(\frac{7}{15}-\frac{5}{12}+\frac{8}{15}\right)\)

\(=\frac{7}{13}.\left(1-\frac{5}{12}\right)\)

\(=\frac{7}{13}.\left(\frac{12}{12}-\frac{5}{12}\right)\)

\(=\frac{7}{13}.\frac{7}{12}\)

\(=\frac{49}{156}\)