Đáp án:
1.
A=$\frac{4}{7}$+ $\frac{3}{4}$+ $\frac{2}{7}$+ $\frac{5}{4}$+ $\frac{1}{7}$
A=($\frac{4}{7}$+ $\frac{2}{7}$+ $\frac{1}{7}$) + ($\frac{3}{4}$+ $\frac{5}{4}$
A=$\frac{7}{7}$ + $\frac{8}{4}$ = 1 + 2 =3
B= -$\frac{3}{31}$+(-$\frac{6}{17}$) +$\frac{1}{25}$+ (- $\frac{28}{31}$ ) +(-$\frac{11}{17}$) + (-$\frac{1}{5}$)
B= [(-$\frac{3}{31}$) +(- $\frac{28}{31}$ )]+[(-$\frac{6}{17}$)+(-$\frac{11}{17}$)] + $\frac{1}{25}$+ (-$\frac{1}{5}$)
B=(-$\frac{31}{31}$) + (-$\frac{17}{17}$) + $\frac{1}{25}$+ (-$\frac{1}{5}$)
B=-1+(-1)+$\frac{1}{25}$ -$\frac{1}{5}$
B=-2+$\frac{1}{25}$ -$\frac{1}{5}$
B=$\frac{-50}{25}$+$\frac{1}{25}$-$\frac{5}{25}$
B=$\frac{-50+1-5}{25}$ =$\frac{-54}{25}$
Bài 2:
-$\frac{19}{6}$+(-$\frac{15}{2}$ )+$\frac{11}{3}$ < x< -$\frac{5}{4}$ +$\frac{19}{12}$ +(-$\frac{10}{3}$ )
-$\frac{19}{6}$+(-$\frac{45}{6}$ )+$\frac{22}{6}$ < x< -$\frac{15}{12}$ +$\frac{19}{12}$ +(-$\frac{40}{12}$ )
$\frac{-19}{6}$-$\frac{45}{6}$ )+$\frac{22}{6}$ < x< $\frac{-15}{12}$ +$\frac{19}{12}$ -$\frac{40}{12}$ )
$\frac{-19-45+22}{6}$< x< $\frac{-15+19-40}{12}$
$\frac{-42}{6}$< x< $\frac{-36}{12}$
-7< x < -3
=> x ∈ {-4; -5; -6}
cho mik 5 sao + câu trả lời hay nhất+ cảm ơn nha
