wiz-icon
MyQuestionIcon
MyQuestionIcon
16
You visited us 16 times! Enjoying our articles? Unlock Full Access!
Question

If a, b, c are positive rational numbers such that a > b > c and the quadratic equation
(a+b−2c)x2+(b+c−2a)x+(c+a−2b)=0 has a root in the interval (-1, 0), then


A

b + c > a

loader
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B

c + a < 2b

loader
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
C

both roots of the given equation ae rational

loader
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
D

the equaiton ax2+2bx+c=0 has both negative real roots

loader
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
Open in App
Solution

The correct options are
B

c + a < 2b


C

both roots of the given equation ae rational


D

the equaiton ax2+2bx+c=0 has both negative real roots


a>b>c ...(i)
and given equation is
(a+b−2c)x2+(b+c−2a)x+(c+a−2b)=0 ...(ii)
∵ Eq. (ii) has a root in the interval (-1, 0)
∴ f (-1) f(0) < 0
⇒(2a−b−c)(c+a−2b)<0 ...(iii)
From Eq. (i)
a>b⇒a−b>0
and a>c⇒a−c>0∴2a−b−c>0 .... (iv)
From Eqs. (iii) and (iv),
c+a−2b<0
or c+a<2b. ∴ Alternate (b) is correct
Discriminant of Eq. (ii)
=(b+c−2a)2−4(a+b−2c)(c+a−2b)={(b−a)+(c−a)}2−4{(a−c)+(b−c)}{c−b+a−b}={(c−a)−(a−b)}2−4{(b−c)−(c−a)}×{(a−b)−(b−c)}If b−c=X,c−a=Y and a−b=Z
then, discriminant=(Y−Z)2−4(X−Y)(Z−X)=(2X−Y−Z)2 (∵X+Y+Z=0)=(0+3X)2=9X2=9(b−c)2
∴ Both roots of the given equation are rational.
Alternate (c) is correct.
If roots of ax2+2bx+c=0 are α and β
Then α+β=−2ba<0∴α+β<0 and αβ=ca>0 (∵a>b>c)
and discriminant of
ax2+2bx+c=0is 4b2−4ac>0 (∵b>c and b<a)
Hence, roots of ax2+2bx+c=0 are negative and real.
Alternative (d) is correct


flag
Suggest Corrections
thumbs-up
0
Join BYJU'S Learning Program
similar_icon
Related Videos
thumbnail
lock
Nature and Location of Roots
MATHEMATICS
Watch in App
Join BYJU'S Learning Program
CrossIcon
footer-image