chịu

Đặt \(2000=a\)

\(A=a^9\\ B=\left(a-4\right)\left(a-3\right)\left(a-2\right)\left(a-1\right)a\left(a+1\right)\left(a+2\right)\left(a+3\right)\left(a+4\right)\\ B=\left(a^2-16\right)\left(a^2-9\right)\left(a^2-4\right)\left(a^2-1\right)a< a.a^2.a^2.a^2.a^2=a^9\\ B=\left(a-8\right)\left(a-6\right)\left(a-4\right)\left(a-2\right)a\left(a+2\right)\left(a+4\right)\left(a+6\right)\left(a+8\right)\\ C=\left(a^2-64\right)\left(a^2-36\right)\left(a^2-16\right)\left(a^2-4\right)a\\ C< \left(a^2-9\right)\left(a^2-4\right)\left(a^2-1\right)a< a.a^2.a^2.a^2=a^9\\ D=\left(a-20\right)\left(a-15\right)\left(a-10\right)\left(a-5\right)a\left(a+5\right)\left(a+10\right)\left(a+15\right)\left(a+20\right)\\ D=\left(a^2-400\right)\left(a^2-225\right)\left(a^2-100\right)\left(a^2-25\right)a\\ D< \left(a^2-64\right)\left(a^2-36\right)\left(a^2-16\right)\left(a^2-4\right)a< a.a^2.a^2.a^2=9\)

Vậy \(D< C< B< A\)

\(1.\) 12 x 11 + 21 x 11 x 11 + 11 x 33

= ( 12 x 11 ) + ( 21 x 11 x 11 ) + ( 11 x 33 )

= \(132+2541+363\)

= \(3036\)

132x11-11x32-54x11

= ( 132 x 11 ) - ( 11 x 32 ) - ( 54 x 11 )

\(=1452-352-594\)

= \(506\)

\(2.\)

45 x 32 + 1245

= ( 45 x 32 ) + 1245

= 1400 + 1245

= 2685

75 x 18 + 75 x 21

= ( 75 x 18 ) + ( 75 x 21 )

= 1350 + 1575

= 2925

12 x (27+46) -1567

= 12 x 73 - 1567

= ( 12 x 73 ) - 1567

= 876 - 1567

= - 691

`(300+70)+500 = 370+500=870`

`300+(70+500)=300+570=870`

`(178+214)+86=392+86=478`

` 178+(214+86)=178+300 = 478`

`b,` Giá trị của biểu thức `(300 + 70) + 500, 300 + (70 + 500)` bằng nhau `(=870)`

`-` Giá trị của biểu thức `(178 + 214) + 86, 178 + (214 + 86)` bằng nhau `(=478)`

`c,` `25+(30+45) = 25+75 = 100`

` (25+30)+45 = 55+45=100`

4:

D=6a+9b=3(2a+3b)=36

5: 

D=15a+5b=5(3a+b)=90

Câu 5:

\(D\left(2\right)=21a+9b-6a-4b\)

\(D\left(2\right)=\left(21a-6a\right)+\left(9b-4b\right)\)

\(D\left(2\right)=15a+5b\)

Mà: \(3a+b=18\Rightarrow b=18-3b\)

\(\Rightarrow D\left(2\right)=15a+5\left(18-3b\right)\)

\(D\left(2\right)=15a+90-15a\)

\(D\left(2\right)=90\)

Vậy: ...

Câu 4:

\(D\left(1\right)=4a+10b-b+2a\)

\(D\left(1\right)=\left(4a+2a\right)+\left(10b-b\right)\)

\(D\left(1\right)=6a+9b\)

Mà: \(2a+3b=12\Rightarrow a=\dfrac{12-3b}{2}\)

\(\Rightarrow D\left(1\right)=6\left(\dfrac{12-3b}{2}\right)+9b\)

\(D\left(1\right)=\dfrac{6\left(12-3b\right)}{2}+9b\)

\(D\left(1\right)=3\left(12-3b\right)+9b\)

\(D\left(1\right)=36-9b+9b\)

\(D\left(1\right)=36\)

Vậy: ...

Câu 3:

Sửa đề: \(C=5a-4b+7a-8b\)

\(C=\left(5a+7a\right)-\left(4b+8b\right)\)

\(C=12a-12b\)

\(C=12\left(a-b\right)\)

\(C=12\cdot8\)

\(C=96\)

Vậy: ...