已知實數(shù)a,b,c,滿足a>0,a^2-2ab+c^2=0,bc>a^2 (1)求證:b>c>0 (2)試確定實數(shù)a,c的大小關(guān)系
(1) a>0, a^2-2ab+c^2=0=>b>0,bc>a^2>0=> c>0
0=a^2-2ab+c^2=(a-b)^2+c^2-b^2=>b^2-c^2=(a-b)^2≥0
=>b≥c>0
若b=c,則b^2-c^2=(a-b)^2=0=>a=b
=>a=b=c=>bc=a^2 與題意bc>a^2矛盾
從而,b>c>0
(2)a^2
ac^2=2ab-a^2>2a^2-a^2=a^2=>c>a
從而b>c>a>0