1. Tìm min, áp dụng \mid A\mid +\mid B\mid \geq \mid A+B\mid
a) A=\sqrt{49x^2-42x+9} + \sqrt{49x^2+126x+81}
b) B=\sqrt{x^2+2y^2-6x+4y+11}+\sqrt{x^2+3y^2+2x+6y+4}
c) C=\mid x-1\mid +\mid 3-x\mid
d) D=\mid 5-2x\mid +\mid 2x-1\mid
e) E=\mid 2x+1\mid +\mid 2x+3\mid
2. Tìm max:
a) A=x+\sqrt{2-x}
b)...