Question

Answer 1

Bài 9:

\(a.x:\left(111-99\right)=17\cdot5\\ x:12=85\\ x=85\cdot12\\ x=1020\\ b.\left(509+355\right):x=840:35\\ 864:x=24\\ x=864:24\\ x=36\)

c. \(x:125=75\) dư 5 

\(x=125\cdot75+5\\ x=9380\) 

d. \(\left(x-15\right):12=79\) dư 8 

\(x-15=12\cdot79+8\\ x-15=956\\ x=956+15\\ x=971\)

Answer 2

Bài 8:

a: \(A=199\cdot201=\left(200-1\right)\left(200+1\right)=200^2-1\)

=>A=B-1

=>A<B

b: \(A=2015\cdot2025\)

\(=\left(2020-5\right)\left(2020+5\right)\)

\(=2020^2-5^2=B-25\)

=>A<B