Question

Tìm x

a) \(\left[\left(6\dfrac{3}{7}-\dfrac{0,75.x-2}{0,35}\right).2,8+1,75\right]:0,05=2,35\)

b) \(\dfrac{3}{5}-\dfrac{2}{7}< \dfrac{2}{3}.x+\dfrac{3}{4}< \dfrac{1}{2}+\dfrac{7}{9}\)

Answer 1

a: Sửa đề: \(\left[\left(6\dfrac{3}{7}-\dfrac{0,75x-2}{0,35}\right)\cdot2.8+1.75\right]\cdot0.05=2.35\)

\(\Leftrightarrow\left(\dfrac{45}{7}-\dfrac{15x-40}{7}\right)\cdot2.8+1,75=47\)

\(\Leftrightarrow\dfrac{45-15x+40}{7}\cdot2,8=45,25\)

\(\Leftrightarrow\dfrac{85-15x}{7}=\dfrac{905}{56}\)

=>8(85-15x)=905

=>680-120x=905

=>120x=-225

hay x=-15/8

b: \(\dfrac{3}{5}-\dfrac{2}{7}< \dfrac{2}{3}x+\dfrac{3}{4}< \dfrac{1}{2}+\dfrac{7}{9}\)

\(\Leftrightarrow\dfrac{11}{35}-\dfrac{3}{4}< \dfrac{2}{3}x< \dfrac{23}{18}-\dfrac{3}{4}\)

\(\Leftrightarrow-\dfrac{61}{140}< \dfrac{2}{3}x< \dfrac{19}{36}\)

\(\Leftrightarrow-\dfrac{183}{280}< x< \dfrac{19}{24}\)