155,9 : 45

 20       3,4

 20 9

   2 9

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\(5x^2y^2-30xy^2+5xy=5xy\left(xy-6y+1\right)\)

\(5x^2y^2-30xy^2+5xy=5xy\left(xy-6y+1\right)\)

xy=7(x-y)=>xy=7x-7y

=>xy-7x+7y=0

=>x(y-7)+7y=0

=>x(y-7)+7y-49=-49

=>x(y-7)+7(y-7)=-49

=>(x+7)(y-7)=-49

xảy ra các trường hợp:

tự làm tiếp nha

b: 

C12: =max(c6:c10)

b: \(\Leftrightarrow n+1\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{0;-2;1;-3;3;-5\right\}\)

c: \(\Leftrightarrow n+2\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{-1;-3;3;-7\right\}\)

d: \(\Leftrightarrow n+2\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{-1;-3;0;-4;2;-6\right\}\)

a: \(\Leftrightarrow n-1\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{2;0;6;-4\right\}\)

b: \(\Leftrightarrow n+1\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{0;-2;1;-3;3;-5\right\}\)

c: \(\Leftrightarrow n+2\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{-1;-3;3;-7\right\}\)

d: \(\Leftrightarrow n+2\in\left\{1;-1;2;-2;4;-4\right\}\)

hay \(n\in\left\{-1;-3;0;-4;2;-6\right\}\)

a: \(\Leftrightarrow n-1\in\left\{1;-1;5;-5\right\}\)

hay \(n\in\left\{2;0;6;-4\right\}\)

a) 13276-(4500+3276)= 13276-4500-3276

                                    = 13276-3276-4500

                                    = 10000-4500=5500

b) 58264+4723-8264-723=58264-8264+4723-723=50000+4000=54000

a) 13726-(4500+3726)=13726-4500-3726=13726-3726-4500=10000-4500=5500

a,, 13 726 - ( 4500 + 3726 )

   = 13 726 - 4500 - 3726 

= (13 726 - 3726 ) - 4500

= 10 000 - 4500

= 5500 

b, 58264 + 4723 - 8264 - 723 

= ( 58264 - 8264 ) + (4723 - 723 )

= 50 00 + 4000

= 54 000