UPSC NDA Math Model Paper 10

Let the correct quadratic equation be ax2+bx+c=0
According to Rohan, the equation is ax2+bx+c1=0 and roots are 9 and 4
So, 9+4=

−b

a

⇒ Sum of roots =13
According to Kabir, the equation is ax2+b1x+c=0 and roots are 5 and −3
So,

c

a

=(5)(−3)=−15
Product of roots =−15
∴ The correct quadratic equation is x2−13x−15=0
Hence, option (4) is correct.