Question

已知b/a+c/a=1,求证b^2+4ac≥0.

Answer 1

/a+c/a=1

b+c=a

b=a-c

b^2+4ac=a^2-2ac+c^2+4ac=a^2+2ac+c^2=(a+c)^2>=0

等号当a=-c,b=2a时成立