Question

câu 3: rút gọn rồi quy đồng

a, 12/36 và -16/ 20               b, 21/ 105 và 35/ 150

Câu 4:

a, 3/10 + 5/10            b, [-27] . 36+ 64 . [-27] + 23 . [ -100]

c, 5/8 + 3/ 12             d, -2/17 + 3/19 + -15/ 17 + 16/19 + 5/6

Answer 1

mai mình thi rồi, các bạn giúp mình với

Answer 2

Chờ tí

Answer 3

Câu 4: 

d) Ta có: \(\dfrac{-2}{17}+\dfrac{3}{19}+\dfrac{-15}{17}+\dfrac{16}{19}+\dfrac{5}{6}\)

\(=\left(-\dfrac{2}{17}-\dfrac{15}{17}\right)+\left(\dfrac{3}{19}+\dfrac{16}{19}\right)+\dfrac{5}{6}\)

\(=-1+1+\dfrac{5}{6}=\dfrac{5}{6}\)

Answer 4

Câu 3:

a,\(\dfrac{12}{36}\) và \(\dfrac{16}{20}\)

 \(\dfrac{12}{36}=\dfrac{1}{3}\)

\(\dfrac{-16}{20}=\dfrac{-4}{5}\)

*Tìm BCNN của 3 và 5 (tự tìm)

MC: 15

\(\dfrac{1}{3}=\dfrac{1.5}{3.5}=\dfrac{5}{15}\)

\(\dfrac{-4}{5}=\dfrac{\left(-4\right).3}{5.3}=\dfrac{-12}{15}\)

\(\Rightarrow\dfrac{5}{15}\) và \(\dfrac{-12}{15}\)

b,\(\dfrac{21}{105}\) và \(\dfrac{35}{150}\)

 \(\dfrac{21}{105}=\dfrac{1}{5}\)

\(\dfrac{35}{150}=\dfrac{7}{30}\)

Vì 30\(⋮\)5

\(\Rightarrow\) MC: 30

\(\dfrac{1}{5}=\dfrac{1.6}{5.6}=\dfrac{6}{30}\)

 

\(\Rightarrow\dfrac{6}{30}\) và \(\dfrac{7}{30}\)

Answer 5

Câu 4

a,\(\dfrac{3}{10}+\dfrac{5}{10}=\dfrac{8}{10}=\dfrac{4}{5}\)

b, (-27) . 36+ 64 . (-27) + 23 .  (-100)

= (-27) . (36 + 64) + 23 . (-100)

= (-27) . 100 + 23 . (-100)

= 27 . (-100) + 23 . (-100)

= (-100) . (27 + 23)

= (-100) . 50

= -5000

c,\(\dfrac{5}{8}+\dfrac{3}{12}=\dfrac{5}{8}+\dfrac{1}{4}=\dfrac{5}{8}+\dfrac{2}{8}=\dfrac{7}{8}\)

d,\(\dfrac{-2}{17}+\dfrac{3}{19}+\dfrac{-15}{17}+\dfrac{16}{19}+\dfrac{5}{6}=\left(\dfrac{-2}{17}+\dfrac{-15}{17}\right)+\left(\dfrac{3}{19}+\dfrac{16}{19}\right)+\dfrac{5}{6}=-1+1+\dfrac{5}{6}=0+\dfrac{5}{6}=\dfrac{5}{6}\)