6x=5^21 chia 5^19+14-1

6x=25+12-1

6x=36 suy ra x=6

\(\text{7x - x = 5}^{21}:5^{19}+3.2^2-7^0\)

\(\text{(7-1)x=5}^2\text{ + 3. 4 - 1}\)

\(\text{6x = 25 + 12 - 1}\)

\(\text{6x = 36}\)

\(\text{ x = 6}\)

a)7.x-x=5²¹ :5¹⁹ +3.2² -7⁰

  x.(7-1)=5²+12-1

  x.6     =36

  x         =36:6=6

b)7.x-2.x=6¹⁷:6¹⁵+44:11

   x.(7-2)=6²+4

  x.5      =40

 x=40:5=8

may cai bai day ma cung khong biet oc cho

a) 89-(73-x)=20

=>73-x=89-20

=>73-x=69

=>x=73-69

=>x=4

e, 2^x.4 = 128

<=> 2^x . 2² = 2⁷

=> x + 2 = 7

<=> x = 5

Vậy x = 5

f , ( x - 5)⁴ = (x - 5)⁶

<=> ( x - 5)⁴ - (x - 5)⁶ =0

<=> (x - 5)⁴. [1 - (x - 5)²] = 0

<=> (x - 5)⁴ (1 - x + 5)(1 + x - 5) = 0

<=> (x - 5)⁴ (6 - x)(x - 4) = 0

<=> \(\left[{}\begin{matrix}x-5=0\\6-x=0\\x-4=0\end{matrix}\right.\) <=> \(\left[{}\begin{matrix}x=5\\x=6\\x=4\end{matrix}\right.\)

Vậy x ={5; 6; 4}

49 . 7^x = 2041

<=> 7². 7^x = 7⁴

=> 2 + x = 4

<=> x = 2

Vậy x = 2

7x-10=2 mũ 2

7x-10=4

7x=14

x=2

7x - 10 = 2⁷ : 2⁵

=> 7x - 10 = 2²

=> 7x - 10 = 4

=> 7x = 14

=> x = 2

\(\Rightarrow\left(7x-11\right)^3=\left(2\cdot5\right)^5+200=10^5+200\\ \Rightarrow\left(7x-11\right)^3=10000+200=10200\\ \Rightarrow7x-11=\sqrt[3]{10200}\\ \Rightarrow x=\dfrac{\sqrt[3]{10200}+11}{7}\)

f) \(\left(x-5\right)^4=\left(x-5\right)^6\)

\(\Rightarrow\left[{}\begin{matrix}x-5=0\\x-5=1\\x-5=-1\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=5\\x=6\\x=4\end{matrix}\right.\)

1: x^2-9x+8=0

=>(x-1)(x-8)=0

=>x=1 hoặc x=8

2: 3x^2-7x+4=0

=>3x^2-3x-4x+4=0

=>(x-1)(3x-4)=0

=>x=4/3 hoặc x=1

3: 2x^2+5x-7=0

=>(2x+7)(x-1)=0

=>x=1 hoặc x=-7/2

4: 3x^2-9x+6=0

=>x^2-3x+2=0

=>x=1 hoặc x=2

5: x^2+2x-3=0

=>(x+3)(x-1)=0

=>x=-3 hoặc x=1

`@` `\text {Answer}`

`\downarrow`

`1)`

\(x^2 - 9x + 8?\)

\(x^2-9x+8=0\)

`<=>`\(x^2-8x-x+8=0\)

`<=> (x^2 - 8x) - (x - 8) = 0`

`<=> x(x - 8) - (x-8) = 0`

`<=> (x-1)(x-8) = 0`

`<=>`\(\left[{}\begin{matrix}x-1=0\\x-8=0\end{matrix}\right.\)

`<=>`\(\left[{}\begin{matrix}x=1\\x=8\end{matrix}\right.\)

Vậy, nghiệm của đa thức là `S = {1; 8}`

`2)`

\(3x^2 - 7x + 4 =0\)

`<=> 3x^2 - 3x - 4x + 4 = 0`

`<=> (3x^2 - 3x) - (4x - 4) = 0`

`<=> 3x(x - 1) - 4(x - 1) = 0`

`<=> (3x - 4)(x-1) = 0`

`<=>`\(\left[{}\begin{matrix}3x-4=0\\x-1=0\end{matrix}\right.\)

`<=>`\(\left[{}\begin{matrix}3x=4\\x=1\end{matrix}\right.\)

`<=>`\(\left[{}\begin{matrix}x=\dfrac{4}{3}\\x=1\end{matrix}\right.\)

Vậy, nghiệm của đa thức là `S = {4/3; 1}`

`3)`

\(2x^2 + 5x - 7=0\)

`<=> 2x^2 - 2x + 7x - 7 = 0`

`<=> (2x^2 - 2x) + (7x - 7) = 0`

`<=> 2x(x - 1) + 7(x - 1) = 0`

`<=> (2x+7)(x-1) = 0`

`<=>`\(\left[{}\begin{matrix}2x+7=0\\x-1=0\end{matrix}\right.\)

`<=>`\(\left[{}\begin{matrix}2x=-7\\x=1\end{matrix}\right.\)

`<=>`\(\left[{}\begin{matrix}x=-\dfrac{7}{2}\\x=1\end{matrix}\right.\)

Vậy, nghiệm của đa thức là `S = {-7/2; 1}.`

1. \(A+7x^2y-5xy^2-xy=x^2y+8xy^2-5xy\)

\(\Rightarrow A+7x^2y-x^2y-5xy^2-8xy^2-xy+5xy=0\)

\(\Rightarrow A+6x^2y-13xy^2+4xy=0\)

\(\Rightarrow A=-6x^2y+13xy^2-4xy\)

2. \(4xy^2-7x+1-A=3x^2-7x-1\)

\(\Rightarrow4xy^2-3x^2-7x+7x+1+1-A=0\)

\(\Rightarrow4xy^2-3x^2+2-A=0\)

\(\Rightarrow A=4xy^2-3x^2+2\)