Bài `2`
\(a,\dfrac{3}{8}+\left(\dfrac{1}{2}\right)^5:\left(\dfrac{1}{2}\right)^2\\ =\dfrac{3}{8}+\left(\dfrac{1}{2}\right)^{5-2}\\ =\dfrac{3}{8}+\left(\dfrac{1}{2}\right)^3\\ =\dfrac{3}{8}+\dfrac{1}{8}\\ =\dfrac{4}{8}\\ =\dfrac{1}{2}\\ b,-\dfrac{2}{9}\cdot\dfrac{3}{7}+\dfrac{4}{7}\cdot\left(-\dfrac{2}{9}\right)\\ =-\dfrac{6}{63}+\left(-\dfrac{8}{63}\right)\\ =-\dfrac{14}{63}\\ =-\dfrac{2}{9}\)
\(c,\) Không nhìn rõ ấy.
\(d,-\left(\dfrac{3}{7}+\dfrac{3}{8}\right)-\left(-\dfrac{3}{8}+\dfrac{4}{7}\right)\\ =-\dfrac{3}{7}-\dfrac{3}{8}+\dfrac{3}{8}-\dfrac{4}{7}\\ =\left(-\dfrac{3}{7}-\dfrac{4}{7}\right)+\left(-\dfrac{3}{8}+\dfrac{3}{8}\right)\\ =-\dfrac{7}{7}+0\\ =-1\)
\(d,\dfrac{11}{15}+3\dfrac{8}{17}+\left(\dfrac{4}{15}-2\dfrac{8}{17}\right)\\ =\dfrac{11}{15}+3\dfrac{8}{17}+\dfrac{4}{15}+2\dfrac{8}{17}\\ =\left(\dfrac{11}{15}+\dfrac{4}{15}\right)+\left(3\dfrac{8}{17}+2\dfrac{8}{17}\right)\\ =1+\dfrac{101}{17}\\ =\dfrac{118}{17}\)
\(3:\left(-\dfrac{3}{2}\right)^2+\dfrac{1}{9}\cdot6^2\\ =3:\dfrac{9}{4}+\dfrac{1}{9}\cdot36\\ =3\cdot\dfrac{4}{9}+4\\ =\dfrac{12}{9}+4\\ =\dfrac{16}{3}\)
Bài `3`
`x+2/3=2 1/3`
`=> x+ 2/3 = 7/3`
`=> x= 7/3 -2/3`
`=>x=5/3`
Vậy `x=5/3`
