2(x^2+y^2+xy-5x-4y+2002)=(x+y-2)^2+(x-3)^2+(y-2)^2+3987>=(x+y-2+3-x+2-y)^2/3+3987=3+3987=3990

=>gtnt=1995

dù là cách nào đi nữa thì kết quả vẫn như nhau

min=1995 khi y=1 x=2

a: Ta có: \(\left(x-3\right)^2-x\left(x+5\right)=9\)

\(\Leftrightarrow x^2-6x+9-x^2-5x=9\)

\(\Leftrightarrow x=0\)

b: Ta có: \(\left(x+2\right)\left(x^2-2x+4\right)-x\left(x^2+2\right)=15\)

\(\Leftrightarrow x^3+8-x^3-2x=15\)

\(\Leftrightarrow2x=-7\)

hay \(x=-\dfrac{7}{2}\)

a) mình ko biết làm

b)\(8^x\cdot8^5=8^{25}\)

\(8^x=8^{25}:8^5=8^{20}\Rightarrow x=20\)

bài đó mà cũng không biết ,mày không khờ tới mức đó phải không

a. 6x² - (2x + 5)(3x - 2) = 7

<=> 6x² - 6x² + 4x - 15x + 10 = 7

<=> -11x = -3

<=> \(x=\dfrac{3}{11}\)

b. (5 - x)(25 + 5x + x²) + x(x² - 7) = 25

<=> 125 - x³ + x³ - 7x = 25

<=> -7x = 25 - 125

<=> -7x = -100

<=> \(x=\dfrac{100}{7}\)

c. (7 - 2x)² + (3 + 2x)(3 - 2x) = 30

<=> 49 - 28x + 4x² + 9 - 4x² = 30

<=> 4x² - 4x² - 28x = 30 - 49 - 9

<=> -28x = -28

<=> x = 1

\(1+3+5+7+...+x=1600\)

\(\left(x+1\right).\left[\left(x-1\right)\div2+1\right]\div2=1600\)

\(\left(x+1\right).\left[\frac{x-1}{2}+1\right]=1600.2\)

\(\left(x+1\right).\left[\frac{x-1+2}{2}\right]=3200\)

\(\left(x+1\right).\left[\frac{x+1}{2}\right]=3200\)

\(\frac{\left(x+1\right).\left(x+1\right)}{2}=3200\)

\(\frac{\left(x+1\right)^2}{2}=3200\)

\(\left(x+1\right)^2=3200.2\)

\(\left(x+1\right)^2=6400\)

\(\left(x+1\right)^2=80^2\)

\(x+1=80\)

\(x=79\)

Ta có : 1 + 3 + 5 +7+ ... + x = ( x + 1 )[ ( x - 1 ) : 2 + 1 ] : 2

Mà : 1 + 3 + 5 +7+ ... + x = 1600

=> ( x + 1 )[ ( x - 1 ) : 2 + 1 ] : 2 = 1600

<=> ( x + 1 )[ ( x - 1 ) : 2 + 1 ] = 3200

<=> ( x + 1 ) ( x2−12 + 1 ) = 3200

<=> ( x + 1 ) ( x2+12 ) = 3200

<=> ( x + 1 ) [ ( x + 1 ) : 2 ] = 3200

=>( x + 1 )2 : 2 = 3200

( x + 1 )2 = 6400

=> ( x + 1 )2 = (±80)2

=> x + 1 = ±80

=> x = { 79 ; - 81 }

Mà theo quy luật thì x phải = 0 => x = 79

Vậy x = 79

Ta có :

1 + 3 + 5 + ... + x = 1600

{ ( x - 1 ) / ( 2 ) + 1 } ^ 2 = 1600

( x - 1 ) / ( 2 ) + 1 = 40 ^ 2

( x - 1 ) / ( 2 ) = 40 - 1

( x - 1 ) / ( 2 ) = 39

x - 1 = 39 . 2

x - 1 = 78

x = 78 + 1

x = 79

Vậy x = 79