x + x + x +....+ x + 1+4+7+...+28= 155

có baonhiêu sô trong dãy là có bấy nhiêu số x

(28-1) : 3 + 1 = 10 số

10*x + (tổng ) = 155

tổng = (28+1) x 10 : 2 = 145

10*x + 145 = 155

x  =1

tick nhá

x + (1+4+7+10+.....+28)=155

x + (28+1) . 10 =155

x + 145 =155

suy ra x=155-145=10

Câu 6: D

Câu 7: C

6 D

7 C

8 C

9 D

10 A

11 C

Xét hiệu:

\(\frac{a}{b}-\frac{a+2007}{b+2007}=\frac{a.\left(b+2007\right)-b.\left(a+2007\right)}{b.\left(b+2007\right)}=\frac{ab+2007a-ab+2007b}{b.\left(b+2007\right)}=\frac{2007.\left(a-b\right)}{b.\left(b+2007\right)}\)

Xét 3 trường hợp:

TH1: a=b\(\Rightarrow\)a-b=0\(\Rightarrow\)\(\frac{2007.\left(a-b\right)}{b.\left(b+2007\right)}=\frac{2007.0}{b.\left(b+2007\right)}=0\)\(\Rightarrow\frac{a}{b}=\frac{a+2007}{b+2007}\)

TH2:  a<b\(\Rightarrow\)a-b<0\(\Rightarrow\)\(2007.\left(a-b\right)< 0\Rightarrow\frac{2007.\left(a-b\right)}{b.\left(b+2007\right)}< 0\)\(\Rightarrow\frac{a}{b}< \frac{a+2007}{b+2007}\)

TH3: a>b\(\Rightarrow\)a-b>0\(\Rightarrow\)\(2007.\left(a-b\right)>0\Rightarrow\frac{2007.\left(a-b\right)}{b.\left(b+2007\right)}>0\)\(\Rightarrow\frac{a}{b}>\frac{a+2007}{b+2007}\)

Vậy với a=b thì  \(\frac{a}{b}=\frac{a+2007}{b+2007}\)

            a<b thì \(\frac{a}{b}< \frac{a+2007}{b+2007}\)

           a>b thì  \(\frac{a}{b}>\frac{a+2007}{b+2007}\)

mấy bạn giúp mình với >.<

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ta có 1 = 1 x 1 

ta xét 1 Th 

x + 1= 1 

=> x= 0 

và y - 2 = 1 

=> y = 3

Th âm tự xét 

1= (-1) x(-1)

(x + 1 ) ( y-2) = 1

=> x + 1 = 1 hoặc y - 2 =1

th1 : x + 1 =1

x = 1 -1 

x = 0

th2 : y - 2 = 1

    y = 1 + 2

    y = 3

Vậy : x = 0 ; y = 3

tk mk nha! :)

số âm tương tự nhé !

2

2 nha em

sửa lại:

dáp=> giáp

chôi=> trôi

Cảm ơn anh cj ạ

😊😊😊

?

Đề đâu???

Đề bài bn

GTNN:A=X²+2X+5

             =>A=5

       5=X²+2X+5

       =>X²+2X=0

      =>X=0

GTLN:M=4-/5x-2/-/3-y/

          M=4-/5.0-2/-/ 3-3/

           M=4-2-0=2

           N=5-2x-x²

          N =5-2*0-0²

         N=5

          Mik nghĩ vậy còn bạn sao thì ko bít