đây bạn

Mình ghi kết quả thôi nhé!

a.2/3

b.1/3

c.3/2

d.18

e.21

f.6/5

g.53/60

h.-13/18

           giải

a) 1/3 +1/4 +1/12 = 2/3

b) 3/9 + 12/39 - 1/3  = 1/3

c) 72/36 - 1/2 = 3/2

d) 34 - 32 và 1/2 = 18

e) 68/2 - 52/4 = 21

g) 1/2 + 1/3 + 1/4 - 1/5 = 53/60

h) 32/72 - 21/18 = (-13/18)

Mình làm ngắn gọn nhanh nhất rồi đó, rút gon luôn rồi. nha

mình không hiểu thế nào

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

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

Bài 1: 

a) Ta có: \(x\left(x^2-4\right)=0\)

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

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x-2=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=2\\x=-2\end{matrix}\right.\)

Vậy: \(x\in\left\{0;2;-2\right\}\)

b) Ta có: \(\left(2x-3\right)+\left(-3x\right)-\left(x-5\right)=40\)

\(\Leftrightarrow2x-3-3x-x+5=40\)

\(\Leftrightarrow-2x+2=40\)

\(\Leftrightarrow-2x=38\)

hay x=-19

Vậy: x=-19

Bài 2: 

a) Ta có: \(-45\cdot12+34\cdot\left(-45\right)-45\cdot54\)

\(=-45\cdot\left(12+34+54\right)\)

\(=-45\cdot100\)

\(=-4500\)

b) Ta có: \(43\cdot\left(57-33\right)+33\cdot\left(43-57\right)\)

\(=43\cdot57-43\cdot33+43\cdot33-33\cdot57\)

\(=43\cdot57-33\cdot57\)

\(=57\cdot\left(43-33\right)\)

\(=57\cdot10=570\)