x=99 nên x+1=100

A=x^5-x^4(x+1)+x^3(x+1)-x^2(x+1)+x(x+1)-9

=x^5-x^5-x^4+x^4+...+x^2+x-9

=x-9

=90

P=x3+y3+2xy=(x+y)3−3xy(x+y)+2xy=2013−601xy" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">P=x3+y3+2xy=(x+y)3−3xy(x+y)+2xy=2013−601xy

S=xy=x(201−x)" role="presentation" style="border:0px; direction:ltr; display:inline-table; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">S=xy=x(201−x)

1≤x≤200" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">1≤x≤200

S=200−(x−1)(x−200)≥0⇒Smin=200" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">S=200−(x−1)(x−200)≥0⇒Smin=200

x≤y⇒x≤100" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">x≤y⇒x≤100

S=100.101−(x−100)(x−101)≤100.101⇒Smax=100.101" role="presentation" style="border:0px; direction:ltr; display:inline-block; float:none; font-size:16.38px; line-height:0; margin:0px; max-height:none; max-width:none; min-height:0px; min-width:0px; padding:1px 0px; position:relative; white-space:nowrap; word-spacing:normal; word-wrap:normal" class="MathJax_CHTML mjx-chtml">S=100.101−(x−100)(x−101)≤100.101⇒Smax=100.101

x = 99 suy ra 100 = x +1

A= x^5 - (x + 1)x^4 + (x + 1)x^3 - (x+1)x^2 + (x +1)x - 9

A= x^5 - x^5 - x^4 + x^4 +x^3 - x^3 -x^2 +x^2 + x - 9

A= x - 9 = 99 - 9 = 90

x=99 suy ra 100 = x+1

A= x^(x+1)x^4+(x+1)x^3-(x+1)x^2+(x+1)x-9

A=x^5(x^5-x^4+x^4+x^3-x^2_x^2_9

A=x-9=99-9=90

A-90

ta có A= x⁵-x⁴-99x⁴+99x³+x³-x²-99x²+99x+x-9

A=x⁴.(x-1)-99x³.(x-1)+x².(x-1)-99x.(x-1)+x-9

A= (x-1)(x⁴-99x³+x²-99x)+x-9

A= (x-1)(x-99)(x³+x)+x-9
Thay x=99 vào A ta được: cái này tự thay nhé
ta thấy 99-99=0

<=> A=99-9=90 

bạn like giúp mình với nhé, mình cảm ơn ạ

Ta có x = 99

=> x + 1 = 100

Khi đó A = x⁵ - 100x⁴ + 100x³ - 100x² + 100x - 9

= x⁵ - (x + 1)x⁴ + (x + 1)x³ - (x + 1)x² + (x + 1)x - 9

= x⁵ - x⁵ - x⁴ + x⁴ + x³ - x³ - x² + x² + x - 9

= x - 9 

Thay x = 99 vào A 

=> A = x - 9 = 99 - 9 = 90

Vậy A = 90

Ta có : \(x=99\Rightarrow100=x+1\)

\(A=x^5-100x^4+100x^3-100x^2+100x-9\)

\(=x^5-\left(x+1\right)x^4+\left(x+1\right)x^3-\left(x+1\right)x^2+\left(x+1\right)x-9\)

\(=x^5-x^5-x^4+x^4+x^3-x^3-x^2+x^2+x-9\)

\(=x-9\)hay \(99-9=90\)

Vậy \(A=90\)

Với x = 20040, ta có: A = 10/20040 = 1/2004.

Vậy A = 1/2004 khi x = 20040.