a) \(2.\left(x+\frac{2}{5}\right)+1\frac{1}{4}=\frac{11}{20}\)

\(2.\left(x+\frac{2}{5}\right)+\frac{5}{4}=\frac{11}{20}\)

\(2.\left(x+\frac{2}{5}\right)=\frac{-7}{10}\)

\(x+\frac{2}{5}=\frac{-7}{20}\)

\(x=\frac{-13}{20}\)

Vậy \(x=\frac{-13}{20}\)

b)\(x-1\frac{1}{8}-\frac{2}{3}x-\frac{5}{6}x=75\%\)

  \(\left(x-\frac{2}{3}x-\frac{5}{6}x\right)-\frac{9}{8}=\frac{3}{4}\)

\(\frac{-1}{2}x-\frac{9}{8}=\frac{3}{4}\)

\(\frac{-1}{2}x=\frac{15}{8}\)

\(x=\frac{-15}{4}\)

Vậy \(x=\frac{-15}{4}\)

\(a,2.\left(x+\frac{2}{5}\right)+1\frac{1}{4}=\frac{11}{20}\)

\(2.\left(x+\frac{2}{5}\right)+\frac{5}{4}=\frac{11}{20}\)

\(2.\left(x+\frac{2}{5}\right)=\frac{11}{20}-\frac{5}{4}\)

\(2.\left(x+\frac{2}{5}\right)=\frac{-7}{10}\)

\(x+\frac{2}{5}=\frac{-7}{10}:2\)

\(x+\frac{2}{5}=\frac{-7}{20}\)

\(x=\frac{-7}{20}-\frac{2}{5}\)

\(x=\frac{-3}{4}\)

a) 2(x-3)-3(x-5)=4(3-x)-18

       2x-6-3x-15=12-4x-18

          2x-3x+4x=12-18+6+15

                     3x=15

                       x=15:3

                       x=5

Vậy x=5

Còn phần b đâu bạn?

a,\(2.\left(x-3\right)-3.\left(x-5\right)=4.\left(3-x\right)-18\)

\(=>2x-6-3x+15=12-4x-18\)

\(=>-x+9=-6-4x\)

\(=>-x+4x=-6-9=-15\)

\(=>3x=-15\)

\(=>x=\frac{-15}{3}=-5\)

a, x - 2/5 = -3/4

=> x = -7/20

vậy_

b, 7x - 3/4 = 25%

=> 7x = 25% + 75%

=> 7x = 1

=> x = 1/7

a) 1+2+3+...+2018

=[(2018-1):1+1].(2018+1):2

=2018.2019:2

=2037171

b) 4+7+10+13+...+2017

=[(2017-4):3+1].(2017+4):2

=672.2021:2

=679056

c) 1+2-3-4+5+6-7-8+9+10-11-12+13+14

=(1+2-3-4)+(5+6-7-8)+(9+10-11-12)+13+14

=-4+(-4)+(-4)+13+14

=-12+27

=15

d) 23 x 75 + 25 x 23 + 180

=23 x (75+25) +180

=23 x 100 +180

=2300+180

2480

chúc ban hoc tốt nha

a) Số số hạng: ( 2018 - 1 ) : 1 + 1 = 2018

   Tổng:           2018 x ( 2018 + 1 ) : 2 = 2 037 171

b) Số số hạng: ( 2017 - 4 ) : 3 + 1 = 672

    Tổng: 672 x ( 2017 + 4 ) : 2 = 679 056

giúp mình vs ạ

a) \(\left(2x-3\right)^2-\left(2x+5\right)^2=10\)

\(\Leftrightarrow4x^2-12x+9-4x^2-20x-25-10=0\)

\(\Leftrightarrow-32x-26=0\)

\(\Leftrightarrow-32x=26\)

\(\Rightarrow x=-\frac{13}{16}\)

b) \(4\left(x+1\right)^2+\left(2x-1\right)^2+8\left(x-1\right)\left(x+1\right)=11\)

\(\Leftrightarrow4x^2+8x+4+4x^2-4x+1+8x^2-8=0\)

\(\Leftrightarrow16x^2+4x-3=0\)

\(\Leftrightarrow4\left(4x^2+x+\frac{1}{16}\right)-\frac{13}{4}=0\)

\(\Leftrightarrow\left[2\left(2x+\frac{1}{4}\right)\right]^2-\left(\frac{\sqrt{13}}{2}\right)^2=0\)

\(\Leftrightarrow\left(4x+\frac{1}{2}-\frac{\sqrt{13}}{2}\right)\left(4x+\frac{1}{2}+\frac{\sqrt{13}}{2}\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}4x+\frac{1-\sqrt{13}}{2}=0\\4x+\frac{1+\sqrt{13}}{2}=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{\sqrt{13}-1}{8}\\x=\frac{-1-\sqrt{13}}{8}\end{cases}}\)

c) \(\left(x+5\right)^2=45+x^2\)

\(\Leftrightarrow x^2+10x+25-x^2-45=0\)

\(\Leftrightarrow10x-20=0\)

\(\Leftrightarrow10x=20\)

\(\Rightarrow x=2\)

d) \(\left(2x-3\right)^2-\left(2x-1\right)^2=-3\)

\(\Leftrightarrow4x^2-12x+9-4x^2+4x-1+3=0\)

\(\Leftrightarrow-8x+11=0\)

\(\Leftrightarrow-8x=-11\)

\(\Rightarrow x=\frac{11}{8}\)

e) \(\left(x-1\right)^2-\left(5x-3\right)^2=0\)

\(\Leftrightarrow\left(x-1-5x+3\right)\left(x-1+5x-3\right)=0\)

\(\Leftrightarrow\left(-4x+2\right)\left(6x-4\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}-4x+2=0\\6x-4=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{1}{2}\\x=\frac{2}{3}\end{cases}}\)

a) ( 2x - 3 )² - ( 2x + 5 )² = 10

<=> 4x² - 12x + 9 - ( 4x² + 20x + 25 ) = 10 

<=> 4x² - 12x + 9 - 4x² - 20x - 25 = 10

<=> -32x - 16 = 10

<=> -32x = 26

<=> x = -26/32 = -13/16

b) 4( x + 1 )² + ( 2x - 1 )² + 8( x + 1 )( x - 1 ) = 11

<=> 4( x² + 2x + 1 ) + ( 4x² - 4x + 1 ) + 8( x² - 1 ) = 11

<=> 4x² + 8x + 4 + 4x² - 4x + 1 + 8x² - 8 = 11

<=> 16x² + 4x - 14 = 0

<=> 2( 8x² + 2x - 7 ) = 0

<=> 8x² + 2x - 7 = 0

\(\Delta=b^2-4ac=2^2-4\cdot8\cdot\left(-7\right)=4+224=228\)( không muốn xài delta đâu nhưng bí quá ;-; )

\(\Delta>0\)nên phương trình đã cho có hai nghiệm phân biệt :

\(\hept{\begin{cases}x_1=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-2+\sqrt{228}}{2\cdot8}=\frac{-2+\sqrt{228}}{16}=\frac{-1+\sqrt{57}}{8}\\x_2=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-2-\sqrt{228}}{2\cdot8}=\frac{-2-\sqrt{228}}{18}=\frac{-1-\sqrt{57}}{8}\end{cases}}\)

( Mình nghĩ ý này bạn nên xem lại đề )

c) ( x + 5 )² = 45 + x²

<=> x² + 10x + 25 = 45 + x²

<=> x² + 10x - x² = 45 - 25

<=> 10x = 20

<=> x = 2 

d) ( 2x - 3 )² - ( 2x - 1 )² = -3

<=> 4x² - 12x + 9 - ( 4x² - 4x + 1 ) = -3

<=> 4x² - 12x + 9 - 4x² + 4x - 1 = -3

<=> -8x + 8 = -3

<=> -8x = -11

<=> x = 11/8

e) ( x - 1 )² - ( 5x - 3 )² = 0

<=> [ x - 1 - ( 5x - 3 ) ][ x - 1 + ( 5x - 3 ) ] = 0

<=> [ x - 1 - 5x + 3 ][ x - 1 + 5x - 3 ] = 0

<=> [ -4x + 2 ][ 6x - 4 ] = 0

<=> \(\orbr{\begin{cases}-4x+2=0\\6x-4=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{1}{2}\\x=\frac{2}{3}\end{cases}}\)