Không quy đồng hãy tính hợp lý tổng sau :
\(B=\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
giúp mình với
Không quy đồng mẫu các phân số hãy tính hợp lý gia trị của tổng sau :
\(B=\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}.\)
\(\frac{1}{7}B=\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\)
\(\frac{1}{7}B=\frac{1}{2}-\frac{1}{7}+...+\frac{1}{15}-\frac{1}{28}\)
\(\frac{1}{7}B=\frac{1}{2}-\frac{1}{28}=\frac{13}{28}\)
\(\Rightarrow B=\frac{13}{28}.7=\frac{13}{4}\)
Không quy đồng mẫu, hãy tính hợp lý tổng:
B= \(\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
B = \(\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
B = \(7.\left(\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\right)\)
B = \(7.\left(\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}\right)\)
B = \(7.\left(\frac{1}{2}-\frac{1}{28}\right)\)
B = \(7.\frac{13}{28}\)
B = \(\frac{13}{4}\)
cho mình hỏi viết phân số kiểu gì zợ?
Không quy đồng hãy tính hợp lý các tổng sau :
a) A=\(\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)
b) B=\(\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
không quy đồng hãy tính hợp lí các tổng sau :
a) A = \(\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)
b) B = \(\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
\(a,A=\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)
\(=\frac{-1}{4.5}+\frac{-1}{5.6}+\frac{-1}{6.7}+\frac{-1}{7.8}+\frac{-1}{8.9}+\frac{-1}{9.10}\)
\(=\frac{-1}{4}+\frac{1}{5}-\frac{1}{5}+\frac{1}{6}-...-\frac{1}{9}+\frac{1}{10}\)
\(=-\frac{1}{4}+\frac{1}{10}\)
\(=-\frac{3}{20}\)
\(b,B=\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
\(\frac{B}{7}=\frac{5}{2.7}+\frac{4}{11.7}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\)
\(=\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-....-\frac{1}{28}\)
\(=\frac{1}{2}-\frac{1}{28}=\frac{13}{28}\)
a) \(A=\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)
\(\Rightarrow-1.A=\frac{1}{20}+\frac{1}{30}+........+\frac{1}{90}\)
\(=\frac{1}{4.5}+\frac{1}{5.6}+........+\frac{1}{9.10}\)
\(=\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+........+\frac{1}{9}-\frac{1}{10}=\frac{1}{4}-\frac{1}{10}=\frac{3}{20}\)
\(\Rightarrow A=\frac{3}{20}:\left(-1\right)=\frac{-3}{20}\)
b) \(B=\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
\(\Rightarrow\frac{1}{7}B=\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\)
\(=\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}\)
\(=\frac{1}{2}-\frac{1}{28}=\frac{13}{28}\)
\(\Rightarrow B=\frac{13}{28}:\frac{1}{7}=\frac{13}{28}.7=\frac{13}{4}\)
Bài giải
a, \(A=\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)
\(-1A=\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\)
\(-1A=\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}+\frac{1}{9\cdot10}\)
\(-1A=\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{7}-\frac{1}{8}+\frac{1}{8}-\frac{1}{9}+\frac{1}{9}-\frac{1}{10}\)
\(-1A=\frac{1}{4}-\frac{1}{10}\)
\(-1A=\frac{3}{20}\)
\(A=\frac{3}{20\text{ }}\text{ : }\left(-1\right)=-\frac{3}{20}\)
b, \(B=\frac{5}{2\cdot1}+\frac{4}{1\cdot11}+\frac{3}{11\cdot2}+\frac{1}{2\cdot15}+\frac{13}{15\cdot4}\)
\(\frac{1}{7}B=\frac{5}{2\cdot7}+\frac{4}{7\cdot11}+\frac{3}{11\cdot14}+\frac{1}{14\cdot15}+\frac{13}{15\cdot28}\)
\(\frac{1}{7}B=\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}\)
\(\frac{1}{7}B=\frac{1}{2}-\frac{1}{28}\)
\(\frac{1}{7}B=\frac{13}{28}\)
\(B=\frac{13}{28}\text{ : }\frac{1}{7}=\frac{13}{4}\)
không quy đồng hãy tính hợp lý các tổng sau :
a, A =\(\frac{-1}{20}+\frac{-1}{30}+\frac{-1}{42}+\frac{-1}{56}+\frac{-1}{72}+\frac{-1}{90}\)
b, B=\(\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
a) A = \(\frac{1}{5}\) - \(\frac{1}{4}\)+ \(\frac{1}{6}\)- \(\frac{1}{5}\)+ \(\frac{1}{7}\)-\(\frac{1}{6}\)+\(\frac{1}{8}\)-\(\frac{1}{7}\)+\(\frac{1}{9}\)- \(\frac{1}{8}\)+ \(\frac{1}{10}\)- \(\frac{1}{9}\)
= \(\frac{-1}{4}\)+\(\frac{1}{10}\)= \(\frac{-6}{40}\)= \(\frac{-3}{20}\)
b) B = \(\frac{5}{2.1}\)+ \(\frac{1}{11}\)(4 + \(\frac{3}{2}\)) + \(\frac{1}{2.15}\)(1 + \(\frac{13}{2}\))
= \(\frac{5}{2.1}\)+ \(\frac{1}{11}\).\(\frac{11}{2}\)+ \(\frac{1}{2.15}\).\(\frac{15}{2}\)
= \(\frac{5}{2}\)+ \(\frac{1}{2}\)+ \(\frac{1}{4}\)= 3 + \(\frac{1}{4}\)= \(\frac{13}{4}\)
không quy đồng, tính hợp lý tổng sau
B=\(\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
jup mik ik mik gấp lm mai p nộp bài cô r
minh camon trc nha
bn nk lm nhanh và đúng mừn tít cho nha
Camon niều
B=7(5/2×7+4/7×11+3/11×14+1/14×15+13/15×28)
B=7(1/2-1/7+1/7-1/11+1/11-1/14+1/14-1/15+1/15-1/28)
B=7(1/2-1/28)
B=7×13/28
B=13/4
Làm như thế này đúng rồi mình học rồi mà bạn cứ yên tâm!
Và cho mình xin lỗi máy mình ko viết được phân số xin lỗi nhiều k cho mình nha!
Ai đi ngang cho xin 1 k! Nhà mình nghèo lắm
B:7=5/2.7+4/7.11+3/11.14+1/14.15+13/15.28
B:7=1/2-1/7+1/7-1/11+1/11-1/14+1/14-1/15+1/15-1/28
B:7=1/2-1/28
B:7=13/28
B=13/4
Không quy đồng các phân số hãy tính hợp lý tổng sau : B= 5/2.1 + 4/1.11 + 3/11.2 + 1/2.15 + 13/15.4
\(B=\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
\(\frac{B}{7}=\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.4}\)
\(\frac{B}{7}=\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-...+\frac{1}{15}-\frac{1}{28}\)
\(\frac{B}{7}=\frac{1}{2}-\frac{1}{28}\)
\(\frac{B}{7}=\frac{13}{28}\)
\(B=\frac{13}{28}.7\)
\(B=\frac{13}{4}\)
Tính hợp lý:
\(B=\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
\(\Rightarrow\frac{B}{7}=\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\)
\(=\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}\)
\(=\frac{1}{2}-\frac{1}{28}=\frac{13}{28}\)
\(\Rightarrow B=\frac{13}{28}.7=\frac{13}{4}\)
B=5/2.1+4/1.11+3/11.2+1/2.15+13/15.4
=>1/7.B= 5/2.7+4/7.11+3/11.14+1/14.15+13/15.28
=>1/7.B=1/2-1/7+1/7-1/11+1/11-1/14+1/14-1/15+1/15-1/28
=>1/7.B=1/2-1/28
=>1/7.B=13/28
=>B= 13/28:1/7=13/4
Vậy B=13/4
Quy đồng mẫu các p/s hãy tính hợp lí tổng sau:
B=\(\frac{5}{2.1}\)+\(\frac{4}{1.11}\)+\(\frac{3}{11.2}\)+\(\frac{1}{2.15}\)+\(\frac{13}{15.4}\)