1: Ta có: \(2x\left(x+3\right)-6\left(x-3\right)=0\)

\(\Leftrightarrow2x^2+6x-6x+18=0\)

\(\Leftrightarrow2x^2+18=0\left(loại\right)\)

2: Ta có: \(2x^2\left(2x+3\right)+\left(2x+3\right)=0\)

\(\Leftrightarrow2x+3=0\)

hay \(x=-\dfrac{3}{2}\)

3: Ta có: \(\left(x-2\right)\left(x+1\right)-4x\left(x-2\right)=0\)

\(\Leftrightarrow\left(x-2\right)\left(1-3x\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=2\\x=\dfrac{1}{3}\end{matrix}\right.\)

4: Ta có: \(2x\left(x-5\right)-3x+15=0\)

\(\Leftrightarrow\left(x-5\right)\left(2x-3\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=\dfrac{3}{2}\end{matrix}\right.\)

5: Ta có: \(3x\left(x+4\right)-2x-8=0\)

\(\Leftrightarrow\left(x+4\right)\left(3x-2\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-4\\x=\dfrac{2}{3}\end{matrix}\right.\)

6: Ta có: \(x^2\left(2x-6\right)+2x-6=0\)

\(\Leftrightarrow2x-6=0\)

hay x=3

2:

\(A=\dfrac{x_2-1+x_1-1}{x_1x_2-\left(x_1+x_2\right)+1}\)

\(=\dfrac{3-2}{-7-3+1}=\dfrac{1}{-9}=\dfrac{-1}{9}\)

B=(x1+x2)^2-2x1x2

=3^2-2*(-7)

=9+14=23

C=căn (x1+x2)^2-4x1x2

=căn 3^2-4*(-7)=căn 9+28=căn 27

D=(x1^2+x2^2)^2-2(x1x2)^2

=23^2-2*(-7)^2

=23^2-2*49=431

D=9x1x2+3(x1^2+x2^2)+x1x2

=10x1x2+3*23

=69+10*(-7)=-1

cấy pt dạng ni lớp 8 học rồi mà :v 

chỉ là thêm công thức nghiệm vào thôi ._.

1. ( x + 2 )( x + 4 )( x + 6 )( x + 8 ) + 16 = 0

<=> [ ( x + 2 )( x + 8 ) ][ ( x + 4 )( x + 6 ) ] + 16 = 0

<=> ( x² + 10x + 16 )( x² + 10x + 24 ) + 16 = 0

Đặt t = x² + 10x + 16

pt <=> t( t + 8 ) + 16 = 0

<=> t² + 8t + 16 = 0

<=> ( t + 4 )² = 0

<=> ( x² + 10x + 16 + 4 )² = 0

<=> ( x² + 10x + 20 )² = 0

=> x² + 10x + 20 = 0

Δ' = b'² - ac = 25 - 20 = 5

Δ' > 0 nên phương trình có hai nghiệm phân biệt

\(x_1=\frac{-b'+\sqrt{\text{Δ}'}}{a}=-5+\sqrt{5}\)

\(x_2=\frac{-b'-\sqrt{\text{Δ}'}}{a}=-5-\sqrt{5}\)

Vậy ...

2. ( x + 1 )( x + 2 )( x + 3 )( x + 4 ) - 24 = 0

<=> [ ( x + 1 )( x + 4 ) ][ ( x + 2 )( x + 3 ) ] - 24 = 0

<=> ( x² + 5x + 4 )( x² + 5x + 6 ) - 24 = 0

Đặt t = x² + 5x + 4

pt <=> t( t + 2 ) - 24 = 0

<=> t² + 2t - 24 = 0

<=> ( t - 4 )( t + 6 ) = 0

<=> ( x² + 5x + 4 - 4 )( x² + 5x + 4 + 6 ) = 0

<=> x( x + 5 )( x² + 5x + 10 ) = 0

Vì x² + 5x + 10 có Δ = -15 < 0 nên vô nghiệm

=> x = 0 hoặc x = -5

Vậy ...

3. ( x - 1 )( x - 3 )( x - 5 )( x - 7 ) - 20 = 0

<=> [ ( x - 1 )( x - 7 ) ][ ( x - 3 )( x - 5 ) ] - 20 = 0

<=> ( x² - 8x + 7 )( x² - 8x + 15 ) - 20 = 0

Đặt t = x² - 8x + 7

pt <=> t( t + 8 ) - 20 = 0

<=> t² + 8t - 20 = 0

<=> ( t - 2 )( t + 10 ) = 0

<=> ( x² - 8x + 7 - 2 )( x² - 7x + 8 + 10 ) = 0

<=> ( x² - 8x + 5 )( x² - 7x + 18 ) = 0

<=> \(\orbr{\begin{cases}x^2-8x+5=0\\x^2-7x+18=0\end{cases}}\)

+) x² - 8x + 5 = 0

Δ' = b'² - ac = 16 - 5 = 11

Δ' > 0 nên có hai nghiệm phân biệt 

\(x_1=\frac{-b'+\sqrt{\text{Δ}'}}{a}=-4+\sqrt{11}\)

\(x_2=\frac{-b'+\sqrt{\text{Δ}'}}{a}=-4-\sqrt{11}\)

+) x² - 7x + 18 = 0

Δ = b² - 4ac = 49 - 72 = -23 < 0 => vô nghiệm

Vậy ...

1.(x+2) . (x+4) . (x+6) . (x+8) + 16 = 0

(x+2) . (x+4) . (x+6) . (x+8)         = -16

x⁴ . ( 2 + 4 + 6 + 8 )                    = -16

x⁴ . 20                                         = -16

x⁴                                                          = -16 : 20 

x⁴                                                 = -4 / 5       

x                                                  = \(\sqrt[4]{\frac{-4}{5}}\)

Tk cho mình nhé !!

có cần giải cụ thể không

b: Ta có: \(\left(x+2\right)\left(x+3\right)\left(x+4\right)\left(x+5\right)-24=0\)

\(\Leftrightarrow\left(x^2+7x+10\right)\left(x^2+7x+12\right)-24=0\)

\(\Leftrightarrow\left(x^2+7x\right)^2+22\left(x^2+7x\right)+120-24=0\)

\(\Leftrightarrow x^2+7x+6=0\)

\(\Leftrightarrow\left(x+1\right)\left(x+6\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=-1\\x=-6\end{matrix}\right.\)

Bạn cần viết đề bằng công thức toán (biểu tượng $\sum$ góc trái khung soạn thảo) đẻ được hỗ trợ tốt hơn. Viết như thế kia rất khó đọc => khả năng bị bỏ qua bài cao.

a: =>3x=3

=>x=1

b: =>12x-2(5x-1)=3(8-3x)

=>12x-10x+2=24-9x

=>2x+2=24-9x

=>11x=22

=>x=2

c: =>2x-3(2x+1)=x-6x

=>-5x=2x-6x-3=-4x-3

=>-x=-3

=>x=3

d: =>2x-5=0 hoặc x+3=0

=>x=5/2 hoặc x=-3

e: =>x+2=0

=>x=-2

1: \(2^x=64\)

=>\(x=log_264=6\)

2: \(2^x\cdot3^x\cdot5^x=7\)

=>\(\left(2\cdot3\cdot5\right)^x=7\)

=>\(30^x=7\)

=>\(x=log_{30}7\)

3: \(4^x+2\cdot2^x-3=0\)

=>\(\left(2^x\right)^2+2\cdot2^x-3=0\)

=>\(\left(2^x\right)^2+3\cdot2^x-2^x-3=0\)

=>\(\left(2^x+3\right)\left(2^x-1\right)=0\)

=>\(2^x-1=0\)

=>\(2^x=1\)

=>x=0

4: \(9^x-4\cdot3^x+3=0\)

=>\(\left(3^x\right)^2-4\cdot3^x+3=0\)

Đặt \(a=3^x\left(a>0\right)\)

Phương trình sẽ trở thành:

\(a^2-4a+3=0\)

=>(a-1)(a-3)=0

=>\(\left[{}\begin{matrix}a-1=0\\a-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}a=1\left(nhận\right)\\a=3\left(nhận\right)\end{matrix}\right.\)

=>\(\left[{}\begin{matrix}3^x=1\\3^x=3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\\x=0\end{matrix}\right.\)

5: \(3^{2\left(x+1\right)}+3^{x+1}=6\)

=>\(\left[3^{x+1}\right]^2+3^{x+1}-6=0\)

=>\(\left(3^{x+1}\right)^2+3\cdot3^{x+1}-2\cdot3^{x+1}-6=0\)

=>\(3^{x+1}\left(3^{x+1}+3\right)-2\left(3^{x+1}+3\right)=0\)

=>\(\left(3^{x+1}+3\right)\left(3^{x+1}-2\right)=0\)

=>\(3^{x+1}-2=0\)

=>\(3^{x+1}=2\)

=>\(x+1=log_32\)

=>\(x=-1+log_32\)

6: \(\left(2-\sqrt{3}\right)^x+\left(2+\sqrt{3}\right)^x=2\)
=>\(\left(\dfrac{1}{2+\sqrt{3}}\right)^x+\left(2+\sqrt{3}\right)^x=2\) 

=>\(\dfrac{1}{\left(2+\sqrt{3}\right)^x}+\left(2+\sqrt{3}\right)^x=2\)

Đặt \(b=\left(2+\sqrt{3}\right)^x\left(b>0\right)\)

Phương trình sẽ trở thành:

\(\dfrac{1}{b}+b=2\)

=>\(b^2+1=2b\)

=>\(b^2-2b+1=0\)

=>(b-1)²=0

=>b-1=0

=>b=1

=>\(\left(2+\sqrt{3}\right)^x=1\)

=>x=0

7: ĐKXĐ: \(x^2+3x>0\)

=>x(x+3)>0

=>\(\left[{}\begin{matrix}x>0\\x< -3\end{matrix}\right.\)
\(log_4\left(x^2+3x\right)=1\)

=>\(x^2+3x=4^1=4\)

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

=>(x+4)(x-1)=0

=>\(\left[{}\begin{matrix}x+4=0\\x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=1\left(nhận\right)\\x=-4\left(nhận\right)\end{matrix}\right.\)

\(a,\dfrac{x-3}{x}=\dfrac{x-3}{x+3}\)\(\left(đk:x\ne0,-3\right)\)

\(\Leftrightarrow\dfrac{x-3}{x}-\dfrac{x-3}{x+3}=0\)

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

\(\Leftrightarrow x^2-9-x^2+3x=0\)

\(\Leftrightarrow3x-9=0\)

\(\Leftrightarrow3x=9\)

\(\Leftrightarrow x=3\left(n\right)\)

Vậy \(S=\left\{3\right\}\)

\(b,\dfrac{4x-3}{4}>\dfrac{3x-5}{3}-\dfrac{2x-7}{12}\)

\(\Leftrightarrow\dfrac{4x-3}{4}-\dfrac{3x-5}{3}+\dfrac{2x-7}{12}>0\)

\(\Leftrightarrow\dfrac{3\left(4x-3\right)-4\left(3x-5\right)+2x-7}{12}>0\)

\(\Leftrightarrow12x-9-12x+20+2x-7>0\)

\(\Leftrightarrow2x+4>0\)

\(\Leftrightarrow2x>-4\)

\(\Leftrightarrow x>-2\)

a) ( 4x - 1 ) (x - 3) - ( x - 3 ) ( 5x + 2 ) = 0 

<=>  (x - 3)(4x - 1 - 5x - 2) = 0

<=>  (x - 3)(-x - 3) = 0

<=>  x  = 3 hoặc x = -3

b) ( x + 3 ) ( x - 5 ) + ( x + 3 ) ( 3x - 4) = 0 

<=>  (x + 3)(x - 5 + 3x - 4) = 0

<=>  (x + 3)(4x - 9) = 0

<=>  x = -3 hoặc x = 9/4

c) ( x + 6 ) ( 3x - 1 )+ x² - 36 = 0 

<=>  3x^2 + 17x - 6 + x^2 - 36 = 0

<=>  4x^2 + 17x - 42 = 0

<=>  4x^2 + 24x - 7x - 42 = 0

<=>  4x(x + 6) - 7(x + 6) = 0

<=>  (4x - 7)(x + 6) = 0

<=>  x = -6 hoặc x = 7/4

d) ( x + 4 ) ( 5x + 9 ) - x² + 16 = 0 

<=>  5x^2 + 29x + 36 - x^2 + 16 = 0

<=>  4x^2 + 29x + 52 = 0

<=>  4x^2 + 16x + 13x + 42 = 0

<=>  4x(x + 4) + 13(x + 4) = 0

<=>  (4x + 13)(x + 4) = 0

<=>  x = -13/4 và x = -4

a) \(x^4-x^2+\dfrac{1}{4}-\dfrac{225}{4}=0\\ \left(x^2-\dfrac{1}{2}\right)^2-\dfrac{15}{2}^2=0\\ \left(x+7\right)\left(x-8\right)=0\\ \left[{}\begin{matrix}x=8\\x=-7\end{matrix}\right.\)

Vậy x = 8 hoặc x = -7

a: Ta có: \(x^4-x^2-56=0\)

\(\Leftrightarrow x^4-8x^2+7x^2-56=0\)

\(\Leftrightarrow\left(x^2-8\right)\left(x^2+7\right)=0\)

\(\Leftrightarrow x^2-8=0\)

hay \(x\in\left\{2\sqrt{2};-2\sqrt{2}\right\}\)