Question

[ᴾᴿᴼシPհù♱Tнủγ♱ɧắć♱Áლ☪]

tính một cách hợp lí

a.\(4\frac{3}{4}+\left(-0,37\right)+\frac{1}{8}+\left(-1,28\right)+\left(-2,5\right)+3\frac{1}{12}\)

lưu ý phép tính a ko có phép nhân VD' 4\(\frac{3}{4}\) LÀ hỗn số nhé

b.\(\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\)

c.\(\frac{\frac{5}{22}+\frac{3}{13}-\frac{1}{2}}{\frac{4}{13}-\frac{2}{11}+\frac{3}{2}}\)

Answer 1

[➻❥ทջℴ☪ϑƴ⁀ᶦᵈᵒᶫ]

a.\(4\frac{3}{4}+\left(-0,37\right)+\frac{1}{8}+\left(-1,28\right)+\left(2,5\right)+3\frac{1}{12}\)

\(=\)\(\left(4\frac{3}{4}+\frac{1}{8}+3\frac{1}{12}\right)-\left(0,37+1,28+2,5\right)\)

\(=7\frac{23}{24}-4,15\)

\(=7\frac{23}{24}-4\frac{3}{20}\)

\(=3\frac{97}{120}\)

b.\(\frac{3}{5.7}+\frac{3}{7.9}+...+\frac{3}{59.61}\)

\(=\frac{3}{2}\left(\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{59.61}\right)\)

\(=\frac{3}{2}\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...\frac{1}{59}-\frac{1}{61}\right)\)

\(=\frac{3}{2}\left(\frac{1}{5}-\frac{1}{61}\right)\)

\(=\frac{3}{2}.\frac{56}{305}\)

\(=\frac{84}{305}\)

c.\(\frac{\frac{5}{22}+\frac{3}{13}-\frac{1}{2}}{\frac{4}{13}-\frac{2}{11}+\frac{3}{2}}\)

\(=\frac{\left(\frac{5}{22}+\frac{3}{13}-\frac{1}{2}\right).\left(2.11.13\right)}{\left(\frac{4}{13}-\frac{2}{11}+\frac{3}{2}\right).\left(2.11.13\right)}\)

\(=\frac{65+66-143}{88-52+429}\)

\(=\frac{-12}{465}=\frac{-4}{155}\)