Question

Giúp mk vs mn

 

Answer 1

(1+1/a)(1+1/b)>=9

=>\(\dfrac{a+1}{a}\cdot\dfrac{b+1}{b}>=9\)

=>ab+a+b+1>=9ab

=>a+b+1>=8ab

=>8ab<=2

=>(a+b)^2>=4ab

=>(a-b)^2>=0(luôn đúng)