Q.
Let three quadratic equations ax2−2bx+c=0,bx2−2cx+a=0 and cx2−2ax+b=0, all have only positive roots. Then which of these are always true?
see full answer
Start JEE / NEET / Foundation preparation at rupees 99/day !!
21% of IItians & 23% of AIIMS delhi doctors are from Sri Chaitanya institute !!
An Intiative by Sri Chaitanya
a
b2 = ac
b
c2 = ab
c
each pair of equations has exactly one root common
d
each pair of equations has two roots common
answer is A.
(Unlock A.I Detailed Solution for FREE)
Ready to Test Your Skills?
Check your Performance Today with our Free Mock Test used by Toppers!
Take Free Test
Detailed Solution
For each equation, required conditions(i) Discriminant≥0⇒b2≥ac,c2≥ab,a2≥bc(ii) f(0)>0 ⇒c,a,b>0(iii) Abscissa of vertex > 0 ⇒ba>0,cb>0,ac>0.Now, b2≥ac,c2≥ab⇒b2c2≥a2bc⇒bc≥a2But a2≥bc. So, a2=bc.Similarly, b2 = ac and c2 = ab.Therefore, a = b = c.
Watch 3-min video & get full concept clarity