1. Chứng minh rằng:
a. \(\dfrac{a^2+b^2}{2}\)≥(\(\dfrac{a+b}{2}\))2
b. \(\dfrac{a^2+b^2+c^2}{3}\)≥(\(\dfrac{a+b+c}{3}\))2
2. Chứng minh rằng:
a. a2+\(\dfrac{b^2}{4}\)≥ab
b. (a+b)2≤ 2(a2+b2)
c. a2+b2+1 ≥ ab+a+b
3. Chứng minh rằng: a2+ 5b2-(3a+b) ≥ 3ab-5