quy đồng ra toán này lớp 4 chứ 6 j

7-3=4

tám trăm nhân với bảy là ra

        3/7 *14/5 - 1/2 = 6/5-1/2 = 7/10

        2/5 - 3/5 *5/10 = 2/5  - 3/10 = 1/10

        4/13 *5/11 + 4/13 *6/11 - 4/13

        = 4/13*5/11 +4/13 *6/11 - 4/13 *1

        = 4/13 *(5/11+ 6/11 - 1)

        = 4/13 *0

        =0

là 84 =)

TL

12 và 21 là 2 số nguyên nên mẫu số của chúng luôn luôn là 1

HT Ạ

!!!!!!!!!!!!!!!!

TL*

- 4/5 < -6/18 + - 14/35 

Ht

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\(\frac{-6}{18}\)+\(\frac{-14}{35}\)=-11/15

-4/5=-12/15

Ta có : -12/15<-11/15

=>-4/5   <   -6/18+  -14/35

HT

\(\frac{151515}{353535}=\frac{151515\div10101}{353535\div10101}=\frac{15}{35}\)

Rút gọn là \(\frac{3}{7}\)nhé 

Bài 1 :

a) \(\frac{12}{-18}\)=\(\frac{2}{-3}\)

b)\(\frac{-15}{-35}\)=\(\frac{-3}{-7}\)

c) \(\frac{-22}{-121}\)=\(\frac{2}{11}\)

d)\(\frac{-24}{66}\)=\(\frac{-4}{11}\)

e)\(\frac{72}{-18}\)= \(4\)

f)\(\frac{39}{-27}\)=\(\frac{13}{-9}\)

g)\(\frac{2}{-18}\)=\(\frac{1}{-9}\)

h)\(\frac{-12}{-16}\)=\(\frac{-3}{-4}\)

y)\(\frac{18}{-60}\)=\(\frac{3}{-10}\)

Bài 2 :

a)\(\frac{-3}{8}\)=\(\frac{-3x-9}{8x-9}\)=\(\frac{-27}{-72}\)

\(\frac{2}{-9}\)=\(\frac{2x9}{-9x8}\)=\(\frac{18}{-72}\)

Vậy \(\frac{-3}{8}\)<\(\frac{2}{-9}\)

\(x^2+7=x^2-1+8=\left(x-1\right)\left(x+1\right)+8⋮\left(x+1\right)\Leftrightarrow8⋮\left(x+1\right)\)

\(\Leftrightarrow x+1\inƯ\left(8\right)=\left\{-8,-4,-2,-1,1,2,4,8\right\}\Leftrightarrow x\in\left\{-9,-5,-3,-2,0,1,3,7\right\}\).d\(x^2+8=x^2-4+4=\left(x-2\right)\left(x+2\right)+4⋮\left(x+2\right)\Leftrightarrow4⋮\left(x+2\right)\)

\(\Leftrightarrow x+2\inƯ\left(8\right)=\left\{-4,-2,-1,1,2,4\right\}\Leftrightarrow x\in\left\{-6,-4,-3,-1,0,2\right\}\)

Suy ra \(x\in\left\{-3,0\right\}\).