Flag Algebra> fiitjee rsm question !!!!!!!!!!...
question mark

if c is positive and 2ax2 +3bx + 5c = 0, then prove that 2a -3b + 5c>0

ramesh jain , 12 Years ago
Grade 11
anser 2 Answers
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

 

 

ramesh jain

Last Activity: 12 Years ago

 i found the correct answer buddy that is -

we have two cases f(x)>0 or f(x)<0

now, for F(0)=5c>0

therefroe for all real values of F(x)>0

for F(1)>0

2a -3b +5c >0, hence proved

Provide a better Answer & Earn Cool Goodies

Enter text here...
star
LIVE ONLINE CLASSES

Prepraring for the competition made easy just by live online class.

tv

Full Live Access

material

Study Material

removal

Live Doubts Solving

assignment

Daily Class Assignments


Ask a Doubt

Get your questions answered by the expert for free

Enter text here...