Bài giải

đổi \(\dfrac{1}{4}\)= 0,25

Chu vi mảnh vườn là: (5,5+3,75).2= 18,5 (m)

Số khóm hoa cần trồng là: 18,5 : 0,25 = 74 (khóm hoa)

Vậy số khóm hoa cần trồng là 74 khóm 

a) \(\dfrac{1}{5}+\dfrac{4}{5}:x=0,75\)

\(\dfrac{1}{5}+\dfrac{4}{5}:x=\dfrac{3}{4}\)

\(\dfrac{4}{5}:x=\dfrac{3}{4}-\dfrac{1}{5}\)

\(\dfrac{4}{5}:x=\dfrac{11}{20}\)

\(x=\dfrac{4}{5}:\dfrac{11}{20}=\dfrac{16}{11}\)

b) \(x+\dfrac{1}{2}=1-x\)

\(x+x=1-\dfrac{1}{2}\)

\(2x=\dfrac{1}{2}\)

\(x=\dfrac{1}{2}:2=\dfrac{1}{4}\)

a) \(\dfrac{2}{3}.\dfrac{5}{4}-\dfrac{3}{4}.\dfrac{2}{3}=\dfrac{2}{3}.\left(\dfrac{5}{4}-\dfrac{3}{4}\right)=\dfrac{2}{3}.\dfrac{2}{4}=\dfrac{1}{3}\)

b) 2.\(\left(\dfrac{-3}{2}\right)^2-\dfrac{7}{2}=2.\left(\dfrac{9}{4}\right)-\dfrac{7}{2}=\dfrac{9}{2}-\dfrac{7}{2}=1\)

c) \(-\dfrac{3}{4}.5\dfrac{3}{13}-0,75.\dfrac{36}{13}=-\dfrac{3}{4}.\dfrac{68}{13}-\dfrac{3}{4}.\dfrac{36}{13}=-\dfrac{3}{4}\left(\dfrac{68}{13}+\dfrac{36}{13}\right)=\dfrac{3}{4}.8=6\)