JEE 2023 — Mathematics PYQ
JEE | Mathematics | 2023If the functions f(x)=3x2+2bx+2ax2 and g(x)=3x2+ax+bx2, where a=2b, have a common extreme point, then the value of a+2b+7 is equal to:
Choose the correct answer:
- A.
23
- B.
3
- C.
4
- D.
6
(Correct Answer)
6
Explanation
olution
1. Differentiate the functions:
-
f′(x)=x2+ax+2b
-
g′(x)=x2+2bx+a
2. Set both to zero for a common extreme point x0:
Since both equal zero, we can set them equal to each other:
3. Solve for x0:
Subtract x02 from both sides:
Since a=2b, we can divide both sides by (a−2b):
4. Substitute x0=1 back into either derivative:
Using f′(1)=0:
5. Calculate the final value:
The question asks for a+2b+7:
Explanation
olution
1. Differentiate the functions:
-
f′(x)=x2+ax+2b
-
g′(x)=x2+2bx+a
2. Set both to zero for a common extreme point x0:
Since both equal zero, we can set them equal to each other:
3. Solve for x0:
Subtract x02 from both sides:
Since a=2b, we can divide both sides by (a−2b):
4. Substitute x0=1 back into either derivative:
Using f′(1)=0:
5. Calculate the final value:
The question asks for a+2b+7:

