A = 2 − 5 + 8 − 11 + 14 − 17 + ... + 98 − 101 = 2 − 5 + 8 − 11 + 14 − 17 + ... + 98 − 101 = − 3 + − 3 + − 3 + ... + − 3 = − 3.17 = − 51.

a) \(\left(\dfrac{1}{6}+\dfrac{5}{9}\right)+\dfrac{4}{9}\)

\(=\dfrac{1}{6}+\dfrac{5}{9}+\dfrac{4}{9}\)

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

\(=\dfrac{7}{6}\)

b) \(\dfrac{3}{17}+\left(\dfrac{14}{17}-\dfrac{2}{3}\right)\)

\(=\dfrac{3}{17}+\dfrac{14}{17}-\dfrac{2}{3}\)

\(=1-\dfrac{2}{3}\)

\(=\dfrac{1}{3}\)

c) \(\left(\dfrac{3}{2}-\dfrac{2}{3}\right)+\dfrac{7}{6}\)

\(=\left(\dfrac{9}{6}-\dfrac{4}{6}\right)+\dfrac{7}{6}\)

\(=\dfrac{13}{6}+\dfrac{7}{6}\)

\(=\dfrac{20}{6}\)

E = 2 − 5 + 8 − 11 + 14 − 17 + ... + 98 − 101 = 2 − 5 + 8 − 11 + 14 − 17 + ... + 98 − 101 = − 3 + − 3 + − 3 + ... + − 3 = − 3.17 = − 51.

a/\(30,395:217=0,14\)(dư 0,015)
b/\(\dfrac{5}{7}:\dfrac{9}{14}-\dfrac{17}{18}\)
\(=\dfrac{5}{7}\times\dfrac{14}{9}-\dfrac{17}{18}\)
\(=\dfrac{10}{9}-\dfrac{17}{18}\)
\(=\dfrac{20}{18}-\dfrac{17}{18}\)
\(=\dfrac{3}{18}=\dfrac{1}{6}\)

30395 : 217 = 140

dư 15

Bài 4:

\(A=2x^2-15\ge-15\\ A_{min}=-15\Leftrightarrow x=0\\ B=2\left(x+1\right)^2-17\ge-17\\ B_{min}=-17\Leftrightarrow x=-1\)

Bài 5:

\(A=-x^2+14\le14\\ A_{max}=14\Leftrightarrow x=0\\ B=25-\left(x-2\right)^2\le25\\ B_{max}=25\Leftrightarrow x=2\)