a,

\(x=\dfrac{-3}{10}+\dfrac{2}{5}\)

\(x=\dfrac{1}{10}\)

b,

\(x-\dfrac{1}{2}=\dfrac{11}{4}\cdot\dfrac{5}{11}\)

\(x-\dfrac{1}{2}=\dfrac{5}{4}\)

\(x=\dfrac{5}{4}+\dfrac{1}{2}\)

\(x=\dfrac{7}{4}\)

c,

\(\dfrac{1}{2}.x^2-\dfrac{9}{2}=0\)

\(\dfrac{1}{2}.x^2=\dfrac{9}{2}\)

\(x^2=\dfrac{9}{2}:\dfrac{1}{2}\)

\(x^2=9\)

x = 3

\(\left(\dfrac{3}{5}+\dfrac{4}{3}\right)x=\dfrac{-4}{3}\)

\(\dfrac{29}{15}x=\dfrac{-4}{3}\)

\(x=\dfrac{-4}{3}:\dfrac{29}{15}\)

\(x=\dfrac{-20}{29}\)

3 giờ 15 phút=………3,25……giờ. 2 giờ rưỡi=……150……phút 2,5 thế kỉ=………250…năm 6 mᶟ 25 dmᶟ=……6,025……mᶟ 14,65mᶟ=………14………mᶟ……65………dmᶟ 1045 cmᶟ……1,045…dmᶟ Gấp

ĐKXĐ : x ≠ 3; x ≠ - 3

\(\Rightarrow x\left(x+3\right)-2x-15=5\left(x-3\right)\)

\(\Leftrightarrow x^2+3x-2x-15=5x-15\)

\(\Leftrightarrow x^2-4x=0\)

\(\Leftrightarrow x\left(x-4\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=4\end{matrix}\right.\) (N)

B

phong cách cũ í mè:"))

D

0,5 m2:D