\(\left(2x+\frac{3}{5}\right)^2-\frac{9}{25}=0\)

\(\Leftrightarrow\left(2x+\frac{3}{5}\right)^2=\frac{9}{25}\)

\(\Leftrightarrow\orbr{\begin{cases}2x+\frac{3}{5}=\frac{3}{5}\\2x+\frac{3}{5}=\frac{-3}{5}\end{cases}\Leftrightarrow\orbr{\begin{cases}2x=0\\2x=\frac{-6}{5}\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=0\\x=-\frac{12}{5}\end{cases}}}\)

Vậy \(x=\left\{0;\frac{-12}{5}\right\}\)

Gọi số bi ban đầu trong hộp là x (viên) (x>0)

Theo bài ra: \(x-\frac{2}{3}x+30=\frac{5}{6}x\)

<=> \(\frac{1}{2}x=30\)

<=> \(x=60\)

Vậy lúc đầu trong hộp có 60 viên bi

\(\frac{1}{7}\cdot\frac{2}{9}+\frac{1}{9}\cdot\frac{3}{7}+\frac{1}{7}\cdot\frac{4}{9}\)

\(=\frac{2}{7}\cdot\frac{1}{9}+\frac{1}{9}\cdot\frac{3}{7}+\frac{4}{7}\cdot\frac{1}{9}\)

\(=\frac{1}{9}\left(\frac{2}{7}+\frac{3}{7}+\frac{4}{7}\right)\)

\(=\frac{1}{9}\cdot\frac{9}{7}=\frac{1}{7}\)

\(\frac{1}{7}.\frac{2}{9}+\frac{1}{9}.\frac{3}{7}+\frac{1}{7}.\frac{4}{9}\)

\(=\frac{2}{7}.\frac{1}{9}+\frac{1}{9}.\frac{3}{7}+\frac{4}{7}.\frac{1}{9}\)

\(=\frac{1}{9}.\left(\frac{2}{7}+\frac{3}{7}+\frac{4}{7}\right)\)

\(=\frac{1}{9}.\frac{9}{7}\)

\(=\frac{1}{7}\)

And can you challenge yourself?

LINK:https://olm.vn/hoi-dap/detail/257197188334.html

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

\(=\frac{1}{3}\left(\frac{4}{5}+\frac{6}{5}\right)\)

\(=\frac{1}{3}.2\)

\(=\frac{2}{3}\)

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

\(=\frac{1}{3}.\left(\frac{4}{5}+\frac{6}{5}-1\right)\)

\(=\frac{1}{3}.\left(\frac{4}{5}+\frac{6}{5}-\frac{5}{5}\right)\)

\(=\frac{1}{3}.1\)

\(=\frac{1}{3}\)

\(2)\)\(\frac{3}{7}.\frac{9}{26}-\frac{1}{14}.\frac{1}{13}\)

\(=\frac{1}{7}.\frac{27}{26}-\frac{1}{7}.\frac{1}{26}\)

\(=\left(\frac{27}{26}-\frac{1}{26}\right).\frac{1}{7}\)

\(=1.\frac{1}{7}\)

\(=\frac{1}{7}\)

\(3)\)\(15\left(\frac{1}{5}-\frac{7}{15}+\frac{17}{3}\right)\)

\(=3-7+85\)

\(=81\)

\(4)\)\(38\left(2\frac{1}{19}-5\frac{7}{38}\right)\)

\(=38\left(\frac{39}{19}-\frac{197}{38}\right)\)

\(=78-197\)

\(=-119\)

\(5)\)\(75\left(\frac{-4}{25}+7\frac{1}{15}-5\frac{7}{75}\right)\)

\(=75\left(\frac{-4}{25}+\frac{106}{15}-\frac{382}{75}\right)\)

\(=-12+530-382\)

\(=136\)

Ddaeng

1. Mrs. An feels tired. She'd some hot milk.

2. Will you be free next Sunday morning, Ba? - No, I will visit my grandparents.

3. When the bell rings, everyone goes indoors and classes begin again.

4. Lan doesn't want to go to Hoa's house now because she has to do many assignments.

5. Thanks for helping me with my homework.

\(P\left(x\right)=3x^5+x^4-2x^2+2x-1\)

\(Q\left(x\right)=-3x^5+2x^2-2x+3\)

\(P\left(x\right)+Q\left(x\right)=3x^5+x^4-2x^2+2x-1-3x^5+2x^2-2x+3\)

\(=x^4+2\)

\(P\left(x\right)-Q\left(x\right)=3x^5+x^4-2x^2+2x-1+3x^5-2x^2+2x-3\)

\(=6x^5+x^4-4x^2+4x-4\)

Thu gọn + sắp xếp luôn

P(x) = 3x⁵ + x⁴ - 2x² + 2x - 1

Q(x) = -3x⁵ + 2x² - 2x + 3

P(x) + Q(x) = ( 3x⁵ + x⁴ - 2x² + 2x - 1 ) + ( -3x⁵ + 2x² - 2x + 3 )

                   = ( 3x⁵ - 3x⁵ ) + x⁴ + ( 2x^2 _-- 2x² ) + ( 2x - 2x ) + ( 3 - 1 )

                   = x⁴ + 2

P(x) - Q(x) = ( 3x⁵ + x⁴ - 2x² + 2x - 1 ) - (  -3x⁵ + 2x² - 2x + 3 )

                  = 3x⁵ + x⁴ - 2x² + 2x - 1 + 3x⁵ - 2x² + 2x - 3

                  = ( 3x⁵ + 3x⁵ ) + x⁴ + ( -2x² - 2x² ) + ( 2x + 2x ) + ( -1 - 3 )

                  = 6x⁵ + x⁴ - 4x² + 4x - 4

\(\frac{3}{x-5}=-\frac{4}{x+2}\)

\(\Rightarrow3x+6=-4x+20\)

\(\Rightarrow7x=14\)

\(\Rightarrow x=2\)

\(\frac{3}{x-5}=\frac{-4}{x+2}\)

\(\Rightarrow3\left(x+2\right)=-4\left(x-5\right)\)

\(\Leftrightarrow3x+6=-4x+20\)

\(\Leftrightarrow7x=14\)

\(\Leftrightarrow x=2\)