Question

a)cmr nếu a>b thì 3a+2b≥3b+2a b)(a-b)²≤2(a²+b²) c)(2a-b)²≤5(a²+b²)

Answer 1

a: 3a+2b>=3b+2a

=>3a-2a>=3b-2b

=>a>=b(đúng)

b: =>a^2-2ab+b^2<=2a^2+2b^2

=>2a^2+2b^2-a^2+2ab-b^2>=0

=>(a+b)^2>=0(luôn đúng)

c: =>5a^2+5b^2>=4a^2-4ab+b^2

=>a^2+4ab+4b^2>=0

=>(a+2b)^2>=0(luôn đúng)