(0.5)CHO X ≥ 0; Y ≥ 0 THỎA MÃN 2√X−√Y=1. CHỨNG MINH RẰNG
Câu 5(0.5)Cho x ≥ 0; y ≥ 0 thỏa mãn 2
√
x−√
y=1. Chứng minh rằng: x + y ≥ 15--- Hêt ---
2√
x−22A =( √
x1+1−x−1)
x√
x−√
x+x−1)
:( √
x−11 −12√
x−2): (
(√
x−1)(√
x+1√
x+1)−=√
x+1−√
x(x−1)+x−1(√
x+1)(√
x−1))
¿=
(√
x+1)(x−1x−1)−): √
x1+1(√
x+1)(x−1)=
(√
xx+1)(−2√
xx−1)+1. √
x+1=
x−2√
x+1x−1= √
x−1√
x+1b.
Ta có : x = 3−2√
2 = 2 −2√
2+1 = (√
2−1)2
Thay x = … vao A ta dc:A =