Question

Bài 1: tính hợp lí

a)\(\frac{6}{7}+\frac{1}{7}\times\frac{2}{7}+\frac{1}{7}\times\frac{5}{7}\)

b)\(\frac{1}{4}-\frac{-7}{4}\times\frac{15}{35}\)

 

Answer 1

a/ \(\frac{6}{7}+\frac{1}{7}\times\frac{2}{7}+\frac{1}{7}\times\frac{5}{7}=\frac{6}{7}+\frac{1}{7}\times\left(\frac{2}{7}+\frac{5}{7}\right)=\frac{6}{7}+\frac{1}{7}\times1=\frac{6}{7}+\frac{1}{7}=\frac{7}{7}=1\)

b/ \(\frac{1}{4}-\frac{-7}{4}\times\frac{15}{35}=\frac{1}{4}+\frac{7}{4}\times\frac{3}{7}=\frac{1}{4}+\frac{3}{4}=\frac{4}{4}=1\)

Answer 2

\(\frac{6}{7}+\frac{2}{14}+\frac{5}{14}=\frac{12}{14}+\frac{2}{14}+\frac{5}{14}=\frac{19}{17}\)câu a

câu b \(\frac{1}{4}-\frac{-105}{140}=\frac{35}{140}-\frac{-105}{140}=\frac{140}{140}=1\)

Answer 3

1 nhe bn k minh

Answer 4

cả a và b cùng bang 1

Answer 5

a) 6/7+1/7x2/7+1/7x5/7

=6/7+1/7x(2/7+5/7)

=6/7+1/7x1

=6/7+1/7x7/7=6/7+1/7=1

b)1/4-(-7/4)x15/35=1/4-(-7/4)x3/7=1/4-(-21/28)=1/4+21/28=7/28+21/28=1