Bài 1: Chứng minh rằng:
a) \(a^2+b-2ab\ge0\) b) \(\frac{a^2
+b^2}{2}\ge ab\) c) \(a.\left(a+2\right)< \left(a+1\right)^2\)
d) \(m^2+n^2+2\ge2\left(m+n\right)\) e) \(\left(a+b\right)\left(\frac{1}{a}+\frac{1}{b}\right)\ge4\left(vớia>0,b>0\right)\)