\(;l\\ 54\backslash54\)

a) 1007-0/2=503.5

b)

\(=1+2+\left(5+6-3-4\right)+\left(9+10-7-8\right)+...+\left(29+30-27-28\right)\)

\(=1+2+4+4+...+4\)( có 7 số 4)

\(=3+7\times4=31\)

đáp số là 1 bạn

Câu 1:a) \(\left(\frac{-5}{12}+\frac{6}{11}\right)+\left(\frac{7}{17}+\frac{5}{11}+\frac{5}{12}\right)\)

\(=\left(\frac{-5}{12}+\frac{5}{12}\right)+\left(\frac{6}{11}+\frac{5}{11}\right)+\frac{7}{17}\)

\(=0+1+\frac{7}{17}\)

\(=\frac{17}{17}+\frac{7}{17}\)

\(=\frac{24}{17}\)

b) \(\frac{7}{12}-\left(\frac{5}{12}-\frac{5}{6}\right)\)

\(=\frac{7}{12}-\frac{5}{12}+\frac{5}{6}\)

\(=\frac{7}{12}-\frac{5}{12}+\frac{10}{12}\)

\(=\frac{7-5+10}{12}\)

\(=1\)

c) \(\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}\)

\(=\frac{1}{12}+\frac{1}{30}\)

\(=\frac{5}{60}+\frac{2}{60}\)

\(=\frac{7}{60}\)

Câu 2:a) \(\frac{x}{8}=2+\frac{-3}{2}\)

\(\Leftrightarrow\frac{x}{8}=\frac{4-3}{2}\)

\(\Leftrightarrow\frac{x}{8}=\frac{1}{2}\)

\(\Leftrightarrow2x=8\)

\(\Leftrightarrow x=\frac{8}{2}\)

\(\Leftrightarrow x=4\)

b) \(\frac{-5}{6}+\frac{8}{3}+\frac{29}{-6}\le x\le\frac{-1}{2}+2+\frac{5}{2}\)

\(\Leftrightarrow\frac{-18}{6}\le x\le4\)

\(\Leftrightarrow-3\le x\le4\)

\(\Leftrightarrow x\in\left\{-3;-2;-1;0;1;2;3;4\right\}\)

Lời giải:
ĐKXĐ: $x\geq 5$

$2x^2-8x-6=2\sqrt{x-5}\leq (x-5)+1$ theo BĐT Cô-si

$\Leftrightarrow 2x^2-9x-2\leq 0$

$\Leftrightarrow 2x(x-5)+(x-2)\leq 0$

Điều này vô lý do $2x(x-5)\geq 0; x-2\geq 3>0$ với mọi $x\geq 5$

Vậy pt vô nghiệm nên không có đáp án nào đúng.

a, MSC : 24

   5/8 = 5 x 3/ 8 x 3 = 15/24

   7/12 = 7 x 2/ 12 x 2 = 14/24

b, MSC : 60

  17/15 = 17 x 4/ 15 x 4 = 68/ 60

  29/20 = 29 x 3/ 20 x 3 = 87/ 60

c, MSC : 12

   5/6 = 5 x 2/ 6 x 2 = 10/12

   3/4 = 3 x 3/ 4 x 3 = 9/12

d, MSC : 84

   4/7 = 4 x 12/ 7 x 12 = 48/84

   7/12 = 7 x 7/ 12 x 7 = 49/84

cho mik nha!

Mik cảm ơn!

cho mik nha

A. x = 2

B. \(\dfrac{3}{8}=\dfrac{6}{x}\)\(\Leftrightarrow x=\dfrac{6.8}{3}=16\)

C. x = 3

D. \(x=\dfrac{4.6}{8}=3\)

E. \(x=\dfrac{7}{3}\)

G.\(\dfrac{14}{13}=\dfrac{28}{10-x}\)

<=>\(14\left(10-x\right)=364\)

<=> 10 - x = 26 

<=> x = -16 

H. \(3\left(x+2\right)=4\left(x-5\right)\)

<=> 3x + 6  = 4x - 20 

<=> -x = -26

<=> x = 26

K. \(\dfrac{x}{2}=\dfrac{8}{x}\)

<=> \(x^2=16\)

<=> \(\left[{}\begin{matrix}x=4\\x=-4\end{matrix}\right.\)

M. \(\left(x-2\right)^2=100\)

<=> \(\left[{}\begin{matrix}x-2=10\\x-2=-10\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=12\\x=-8\end{matrix}\right.\)

a=2

b=16

c=3

d=3

mik chỉ biết thế này thôi(ko chắc đúng=3)