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28 tháng 8 2021

\(A=2021-1021:\left(199-x\right)\)

\(\Leftrightarrow A=2021-\frac{1021}{199-x}\)

\(MinA\Leftrightarrow\frac{1021}{199-x}Max\Leftrightarrow199-xMin\Leftrightarrow199-x=1\Leftrightarrow x=199-1\Leftrightarrow x=198\)

Lúc này \(A=2021-1021=100\)

Vậy \(MinA=1000\Leftrightarrow x=198\)

2 tháng 10 2022

địt mẹ mày

 

4 tháng 8 2018

bạn cần câu nào?

AH
Akai Haruma
Giáo viên
19 tháng 12 2021

Lời giải:
$A=x^2+2x+2xy+2y^2+4y+2021$

$=(x^2+2xy+y^2)+2x+y^2+4y+2021$

$=(x+y)^2+2(x+y)+1+(y^2+2y+1)+2019$

$=(x+y+1)^2+(y+1)^2+2019\geq 2019$

Vậy $A_{\min}=2019$ khi $x+y+1=y+1=0$

$\Leftrightarrow (x,y)=(0,-1)$

27 tháng 11 2021
27 tháng 11 2021

?

1 tháng 1 2022

T a space c ó colon space A equals open vertical bar x minus 2021 close vertical bar plus open vertical bar x minus 1 close vertical bar equals open vertical bar 2021 minus x close vertical bar plus open vertical bar x minus 1 close vertical bar
equals greater than A greater or equal than open vertical bar 2021 minus x plus x minus 1 close vertical bar equals open vertical bar 2020 close vertical bar equals 2020 space v ớ i space m ọ i space x
D ấ u space equals space x ả y space r a space less than equals greater than open curly brackets table attributes columnalign left end attributes row cell 2021 minus x greater or equal than 0 end cell row cell x minus 1 greater or equal than 0 end cell end table less than equals greater than open curly brackets table attributes columnalign left end attributes row cell x less or equal than 2021 end cell row cell x greater or equal than 1 end cell end table close close
less than equals greater than 1 less or equal than x less or equal than 2021
V ậ y space v ớ i space 1 less or equal than x less or equal than 2021 space t h ì space A space c ó space G T N N equals 2020

Tham khảo:

T a space c ó colon space A equals open vertical bar x minus 2021 close vertical bar plus open vertical bar x minus 1 close vertical bar equals open vertical bar 2021 minus x close vertical bar plus open vertical bar x minus 1 close vertical bar
equals greater than A greater or equal than open vertical bar 2021 minus x plus x minus 1 close vertical bar equals open vertical bar 2020 close vertical bar equals 2020 space v ớ i space m ọ i space x
D ấ u space equals space x ả y space r a space less than equals greater than open curly brackets table attributes columnalign left end attributes row cell 2021 minus x greater or equal than 0 end cell row cell x minus 1 greater or equal than 0 end cell end table less than equals greater than open curly brackets table attributes columnalign left end attributes row cell x less or equal than 2021 end cell row cell x greater or equal than 1 end cell end table close close
less than equals greater than 1 less or equal than x less or equal than 2021
V ậ y space v ớ i space 1 less or equal than x less or equal than 2021 space t h ì space A space c ó space G T N N equals 2020