AAYUSH KESHAVA
Last Activity: 12 Years ago
REMARK: PLEASE TYPE THE FULL QUESTION(THE ROOTS ARE UNREAL AND c>0)
f(x)=2ax2+3bx+5c=0
SINCE, ROOTS ARE UNREAL.
CASE 1:a>0;D<0 =>9b2-40ac<0 =>9b2<40ac (i)
clearly the rhs of inequality is always positive and so is the lhs
CASE2:a<0;9b2<40ac (ii)
lhs>0 & rhs<0 so not possible
proceeding with case1
we have
f(x),a upper parabola whose vertex is>0,which is also here the minimum value of f(x)
so parabola is always positive
therefore, f(-1)=2a-3b+5c>0
proved