Toán Lớp 5: $\frac{1}{3×6}$ + $\frac{1}{6×9}$ + $\frac{1}{9×12}$ + $\frac{1}{12×15}$
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Toán Lớp 5: $\frac{1}{3×6}$ + $\frac{1}{6×9}$ + $\frac{1}{9×12}$ + $\frac{1}{12×15}$
Comments ( 2 )
=1/3xx(3/(3xx6)+3/(6xx9)+3/(9xx12)+3/(12xx15))
=1/3xx(1/3-1/6+1/6-1/9+1/9-1/12+1/12-1/15)
=1/3xx(1/3-1/15)
=1/3xx(5/15-1/15)
=1/3xx4/15
=4/45