Bài 1:tính hợp lý nếu có thể
a) \(\dfrac{-7}{9}\)+\(\dfrac{5}{12}\)-\(\dfrac{13}{18}\)
b) \(\dfrac{11}{9}\)x\(\dfrac{15}{4}\)-\(\dfrac{11}{4}\)x\(\dfrac{7}{9}\)-\(\dfrac{11}{9}\)x\(\dfrac{5}{4}\)
c) (\(15\dfrac{9}{7}\)+\(6\dfrac{2}{3}\))-\(5\dfrac{5}{9}\)
d) \(\dfrac{5}{6}\)-\(\dfrac{1}{3}\)-\(\dfrac{2}{-18}\)
e) (\(11\dfrac{2}{7}\)+\(3\dfrac{2}{5}\))-\(7\dfrac{2}{7}\)
f) (\(6\dfrac{4}{9}\)+\(3\dfrac{7}{11}\))-\(4\dfrac{4}{9}\)
Đề răng dài thế này thì tui giải từng câu hí
a) \(\dfrac{-7}{9}+\dfrac{5}{12}-\dfrac{13}{18}\left(MSC:36\right)\)
\(=\dfrac{-28}{36}+\dfrac{15}{36}-\dfrac{26}{36}\)
\(=\dfrac{-13}{36}-\dfrac{26}{36}\)
\(=\dfrac{-39}{36}\)
\(=\dfrac{13}{3}\)
b) \(\dfrac{11}{9}.\dfrac{15}{4}-\dfrac{11}{4}.\dfrac{7}{9}-\dfrac{11}{9}.\dfrac{5}{4}\)
\(=\left(\dfrac{15}{4}-\dfrac{11}{4}-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\left(1-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\left(\dfrac{4}{4}-\dfrac{5}{4}\right).\dfrac{11}{9}\)
\(=\dfrac{-1}{4}.\dfrac{11}{9}\)
\(=\dfrac{-11}{36}\)
c) \(\left(15\dfrac{9}{7}+6\dfrac{2}{3}\right)-5\dfrac{5}{9}\)
\(=\left(17+\dfrac{20}{3}\right)-\dfrac{50}{9}\)
\(=\left(\dfrac{51}{3}+\dfrac{20}{3}\right)-\dfrac{50}{9}\)
\(=24-\dfrac{50}{9}\)
\(=\dfrac{216}{9}-\dfrac{50}{9}\)
\(=19\)
d) \(\dfrac{5}{6}-\dfrac{1}{3}-\dfrac{2}{-18}\)
\(=\dfrac{15}{18}-\dfrac{6}{18}-\dfrac{-2}{18}\)
\(=\dfrac{9}{18}-\dfrac{-2}{18}\)
\(=\dfrac{11}{18}\)
Còn 2 câu sáng mai làm
e) \(\left(11\dfrac{2}{7}+3\dfrac{2}{5}\right)-7\dfrac{2}{7}\)
\(=\left(\dfrac{79}{7}+\dfrac{17}{5}\right)-\dfrac{51}{7}\)
\(=\left(\dfrac{395}{35}+\dfrac{119}{35}\right)-\dfrac{51}{7}\)
\(=\dfrac{514}{35}-\dfrac{51}{7}\)
\(=\dfrac{514}{35}-\dfrac{255}{35}\)
\(=\dfrac{259}{35}\)
f) \(\left(6\dfrac{4}{9}+3\dfrac{7}{11}\right)-4\dfrac{4}{9}\)
\(=\left(\dfrac{58}{9}+\dfrac{40}{11}\right)-\dfrac{40}{9}\)
\(=\left(\dfrac{638}{99}+\dfrac{360}{99}\right)-\dfrac{40}{9}\)
\(=10-\dfrac{40}{9}\)
\(=\dfrac{90}{9}-\dfrac{40}{9}\)
\(=\dfrac{50}{9}\)
Có gì sai thông cảm vì không có máy tính :(
