3

\(\dfrac{17}{9}+\dfrac{19}{7}-\dfrac{8}{9}-\dfrac{5}{7}\)

\(=\left(\dfrac{17}{9}-\dfrac{8}{9}\right)+\left(\dfrac{19}{7}-\dfrac{5}{7}\right)=1+2=3\)

3

= 3

Phương pháp giải:

Tính nhẩm từ trái sang phải rồi điền kết quả vào chỗ trống. 

Lời giải chi tiết:

hihihihiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiihhhhiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiihhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiihhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii

_19/9

19/9

Ủa bạn ??

Zậy là tính cả gì vậy

Bài 1:

a: \(\frac{13}{20}<1\)

\(\frac{19}{20}<1\)

\(\frac{17}{23}<1\)

Do đó: \(\frac{13}{20}+\frac{19}{20}+\frac{17}{23}<1+1+1=3\)

hay \(\frac{13}{20}+\frac{19}{20}+\frac{17}{23}<3\)

b: \(\frac75>1;\frac54>1;\frac98>1;\frac32>1\)

Do đó; \(\frac75+\frac54+\frac98+\frac32>1+1+1+1\)

=>\(\frac75+\frac54+\frac98+\frac32>4\)

Bài 2:

\(\frac87+\frac{11}{13}+\frac{23}{30}+\frac{39}{45}<4\)

a: =35/17-18/17-9/5+4/5

=1-1=0

b: =-7/19(3/17+8/11-1)

=7/19*18/187=126/3553

c: =26/15-11/15-17/3-6/13

=1-6/13-17/3

=7/13-17/3=-200/39

\(1\times3\times5\times...\times17\times19=....5\)       (vì 5 nhân với số lẻ nào cũng tận cùng là 5)

\(1\times2\times3\times....\times9=...0\)(vì trong tích có 1 thừa số 5 mà 5 nhân với 1 số chẵn có tận cùng là 0,  một số tận cùng là 0 nhân với số nào cũng tận cùng là 0)

Vậy      \(1\times3\times5\times...\times19+1\times2\times3\times...\times9=...5\)

a) <     b) >     c) <

Bài 1:

a: \(\frac{13}{20}<1\)

\(\frac{19}{20}<1\)

\(\frac{17}{23}<1\)

Do đó: \(\frac{13}{20}+\frac{19}{20}+\frac{17}{23}<1+1+1=3\)

hay \(\frac{13}{20}+\frac{19}{20}+\frac{17}{23}<3\)

b: \(\frac75>1;\frac54>1;\frac98>1;\frac32>1\)

Do đó; \(\frac75+\frac54+\frac98+\frac32>1+1+1+1\)

=>\(\frac75+\frac54+\frac98+\frac32>4\)

Bài 2:

\(\frac87+\frac{11}{13}+\frac{23}{30}+\frac{39}{45}<4\)

\(\dfrac{2}{15}-\dfrac{7}{9}\\ =\dfrac{-29}{45}\\ \dfrac{5}{-12}-\dfrac{-3}{8}\\ =\dfrac{-5}{12}+\dfrac{3}{8}\\ =\dfrac{-1}{24}\)

-29/45; 1/-21 

đấp án đó nhe nhớ tick cho mik