a) \(\dfrac{15-6x}{3}>5\Leftrightarrow15-6x>15\)

\(\Leftrightarrow-6x>0\Leftrightarrow x< 0\) (vì \(-6< 0\))

\(S=\left\{x|x< 0\right\}\)

b) \(\dfrac{8-11x}{4}< 13\Leftrightarrow8-11x< 52\)

\(\Leftrightarrow-11x< -44\Leftrightarrow x>4\) (vì \(-11< 0\))

\(S=\left\{x|x>4\right\}\)

c) \(8x+3\left(x+1\right)>5x-\left(2x-6\right)\)

\(\Leftrightarrow8x+3x+1>5x-2x+6\)

\(\Leftrightarrow8x+3x-5x+2x>6-1\)

\(\Leftrightarrow8x>5\)

\(\Leftrightarrow x>\dfrac{5}{8}\) (vì \(8>0\))

\(S=\left\{x|x>\dfrac{5}{8}\right\}\)

d) \(2x\left(6x-1\right)>\left(3x-2\right)\left(4x+3\right)\)

\(\Leftrightarrow12x^2-2x>12x^2+9x-8x-6\)

\(\Leftrightarrow12x^2-2x-12x^2-9x+8x>-6\)

\(\Leftrightarrow-3x>-6\)

\(\Leftrightarrow x< 2\) (vì \(-3< 0\))

\(S=\left\{x|x< 2\right\}\)

Phát âm - Học trực tuyến OLM

\(\dfrac{2\left(9+2x\right)}{x^2-9}=\dfrac{2}{x-3}-\dfrac{1}{x+3}\)

\(\Leftrightarrow\dfrac{18+4x}{\left(x-3\right)\left(x+3\right)}-\dfrac{2\left(x+3\right)}{\left(x+3\right)\left(x-3\right)}+\dfrac{x-3}{\left(x-3\right)\left(x+3\right)}=0\)

\(\Rightarrow18+4x-2x-6+x-3=0\)

\(\Leftrightarrow3x+9=0\)

\(\Leftrightarrow3\left(x+3\right)=0\)

\(\Leftrightarrow x+3=0\)

\(\Leftrightarrow x=-3\)

\(S=\left\{-3\right\}\)

A. quietly (là trạng từ)

B. friendly (là tính từ)

C. carefully (là trạng từ)

D. quickly (là trạng từ)

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

\(\Leftrightarrow x+\dfrac{16}{5}=4\)

\(\Leftrightarrow x=4-\dfrac{16}{5}\)

\(\Leftrightarrow x=\dfrac{20-16}{5}\)

\(\Leftrightarrow x=\dfrac{4}{5}\)

39. D

40. B

four/and/my/is/bedrooms/has/it/apartment/furnished.

=> My apartment has four bedrooms and it is furnished.

Mỗi hộp có số cốc là: 42 : 7 = 6 (cái cốc).

Để xếp hết 250 cái cốc, cần số hộp là: 250 : 6 = 41 (dư 4 cái cốc).

Nhưng cần xếp 4 cái cốc vào 1 hộp nữa, nên số hộp cần là 41 + 1 = 42 hộp.

Vậy cần ít nhất 42 hộp để xếp hết 250 cái cốc.

\(18\cdot\left(\dfrac{3737}{4242}+\dfrac{3737}{5656}+\dfrac{3737}{7272}\right)\)

\(=18\cdot\left(\dfrac{37\cdot101}{42\cdot101}+\dfrac{37\cdot101}{56\cdot101}+\dfrac{37\cdot101}{72\cdot101}\right)\)

\(=18\cdot\left(\dfrac{37}{42}+\dfrac{37}{56}+\dfrac{37}{72}\right)\)

\(=18\cdot37\cdot\left(\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}\right)\)

\(=18\cdot37\cdot\left(\dfrac{1}{6\cdot7}+\dfrac{1}{7\cdot8}+\dfrac{1}{8\cdot9}\right)\)

\(=666\cdot\left(\dfrac{7-6}{6\cdot7}+\dfrac{8-7}{7\cdot8}+\dfrac{9-8}{8\cdot9}\right)\)

\(=666\cdot\left(\dfrac{7}{6\cdot7}-\dfrac{6}{6\cdot7}+\dfrac{8}{7\cdot8}-\dfrac{7}{7\cdot8}+\dfrac{9}{8\cdot9}-\dfrac{8}{8\cdot9}\right)\)

\(=666\cdot\left(\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}\right)\)

\(=666\cdot\left(\dfrac{1}{6}-\dfrac{1}{9}\right)\)

\(=666\cdot\dfrac{1}{18}\)

\(=37\)

\(\dfrac{-3737}{4141}=\dfrac{-37\cdot101}{41\cdot101}=\dfrac{-37}{41}\)

Mà \(\dfrac{-37}{41}< \dfrac{-34}{41}\) (vì \(-37< -34\))

Nên \(\dfrac{-3737}{4141}< \dfrac{-34}{41}\)