Giúp mik ik ạ mik cảm ơn nhìu
1/3 – 3/5 + 5/7 – 7/9 + 9/11 – 11/13 + 13/15 + 11/13 – 9/11 + 7/9 – 5/7 + 3/5 – 1/3
Giúp mik ik ạ mik cảm ơn nhìu
1/3 – 3/5 + 5/7 – 7/9 + 9/11 – 11/13 + 13/15 + 11/13 – 9/11 + 7/9 – 5/7 + 3/5 – 1/3
Đáp án:
$\dfrac{1}{3}-\dfrac{3}{5}+\dfrac{5}{7}-\dfrac{7}{9}+\dfrac{9}{11}-\dfrac{11}{13}+\dfrac{13}{15}+\dfrac{11}{13}-\dfrac{9}{11}+\dfrac{7}{9}-\dfrac{5}{7}+\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{13}{15}$
Giải thích các bước giải:
$\rm \dfrac{1}{3}-\dfrac{3}{5}+\dfrac{5}{7}-\dfrac{7}{9}+\dfrac{9}{11}-\dfrac{11}{13}+\dfrac{13}{15}+\dfrac{11}{13}-\dfrac{9}{11}+\dfrac{7}{9}-\dfrac{5}{7}+\dfrac{3}{5}-\dfrac{1}{3}\\=\dfrac{1}{3}-\dfrac{1}{3}+\dfrac{5}{7}-\dfrac{5}{7}+\dfrac{9}{11}-\dfrac{9}{11}+\dfrac{13}{15}+\dfrac{11}{13}-\dfrac{11}{13}+\dfrac{7}{9}-\dfrac{7}{9}+\dfrac{3}{5}-\dfrac{3}{5}\\=\left( \dfrac{1}{3}-\dfrac{1}{3}\right)+\left(\dfrac{5}{7}-\dfrac{5}{7}\right)+\left(\dfrac{9}{11}-\dfrac{9}{11}\right)+\dfrac{13}{15}+\left(\dfrac{11}{13}-\dfrac{11}{13}\right)+\left(\dfrac{7}{9}-\dfrac{7}{9}\right)+\left(\dfrac{3}{5}-\dfrac{3}{5}\right)\\=0+0+0+\dfrac{13}{15}+0+0+0\\=\dfrac{13}{15}$
`1/3 – 3/5 + 5/7 – 7/9 + 9/11 – 11/13 + 13/15 + 11/13 – 9/11 + 7/9 – 5/7 + 3/5 – 1/3`
`=(-3/5+3/5)+(5/7-5/7)+(-7/9+7/9)+(9/11-9/11)+(-11/13+11/13)+(1/3-1/3)+13/15`
`=0+0+0+0+0+0+13/15`
`= 13/15`
Học tốt !