NDA 2018 Maths · Mathematics · Derivatives · hard

The parabola y=x^2+ax+b touches the line y=x+1 at the point (2,3). The value of a+b is

Single correct option

The parabola

y=x^2+ax+b

touches the line

y=x+1

at the point

(2,3)

. The value of

a+b

Show answer and solution

Answer: (A) $2$

The point lies on the curve:

4+2a+b=3

. The slopes match at

x=2

2x+a=4+a=1

, so

a=-3

. Then

b=3-4+6=5

and

a+b=2

. The options

-3

and

5

are

a

and

b

individually, and

-15

is their product.

Original question written in the NDA 2018 Maths pattern and checked twice for the correct answer. Not an official question paper. How we write and check questions · Corrections policy · Report a mistake