Toán 1/20+1/30+1/42+1/56+1/72+1/90+1/110+1/132 29/07/2021 By Raelynn 1/20+1/30+1/42+1/56+1/72+1/90+1/110+1/132
`1/20+1/30+1/42+1/56+1/72+1/90+1/110+1/132` `=1/(4xx5)+1/(5xx6)+1/(6xx7)+1/(7xx8)+1/(8xx9)+1/(9xx10)+1/(10xx11)+1/(11xx12)` `=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11+1/11-1/12` `=1/4-1/12` `=1/6` Trả lời
Đáp án: `\frac{1}{6}` Giải thích các bước giải: `\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}+ \frac{1}{132}` `= \frac{1}{4×5}+\frac{1}{5×6}+\frac{1}{6×7}+\frac{1}{7×8}+\frac{1}{8×9}+\frac{1}{9×10}+\frac{1}{10×11}+ \frac{1}{11×12}` `=\frac{1}{4×5}+\frac{1}{5×6}+\frac{1}{6×7}+\frac{1}{7×8}+\frac{1}{8×9}+\frac{1}{9×10}+\frac{1}{10×11}+ \frac{1}{11×12}` `=\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}+ \frac{1}{11}-\frac{1}{12}` `=\frac{1}{4}-\frac{1}{12}` `=\frac{1}{6}` Trả lời
`1/20+1/30+1/42+1/56+1/72+1/90+1/110+1/132`
`=1/(4xx5)+1/(5xx6)+1/(6xx7)+1/(7xx8)+1/(8xx9)+1/(9xx10)+1/(10xx11)+1/(11xx12)`
`=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10+1/10-1/11+1/11-1/12`
`=1/4-1/12`
`=1/6`
Đáp án:
`\frac{1}{6}`
Giải thích các bước giải:
`\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}+ \frac{1}{132}`
`= \frac{1}{4×5}+\frac{1}{5×6}+\frac{1}{6×7}+\frac{1}{7×8}+\frac{1}{8×9}+\frac{1}{9×10}+\frac{1}{10×11}+ \frac{1}{11×12}`
`=\frac{1}{4×5}+\frac{1}{5×6}+\frac{1}{6×7}+\frac{1}{7×8}+\frac{1}{8×9}+\frac{1}{9×10}+\frac{1}{10×11}+ \frac{1}{11×12}`
`=\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{11}+ \frac{1}{11}-\frac{1}{12}`
`=\frac{1}{4}-\frac{1}{12}`
`=\frac{1}{6}`