NIMCET 2013 — Mathematics PYQ
NIMCET | Mathematics | 2013The minimum value of the function y=2x3−21x2+36x−20 is:
Choose the correct answer:
- A.
−120
- B.
−126
- C.
−128
(Correct Answer) - D.
None of these
−128
Explanation
Solution
1. Find the first derivative (y′):
2. Find critical points by setting dxdy=0:
Dividing by 6:
Points are x=1 and x=6.
3. Use the second derivative test to find the minimum:
-
At x=1: \frac{d^2y}{dx^2} = 12(1) - 42 = -30 < 0 (Local Maximum)
-
At x=6: \frac{d^2y}{dx^2} = 12(6) - 42 = 72 - 42 = 30 > 0 (Local Minimum)
4. Calculate the minimum value at x=6:
Substitute x=6 into the original function:
Explanation
Solution
1. Find the first derivative (y′):
2. Find critical points by setting dxdy=0:
Dividing by 6:
Points are x=1 and x=6.
3. Use the second derivative test to find the minimum:
-
At x=1: \frac{d^2y}{dx^2} = 12(1) - 42 = -30 < 0 (Local Maximum)
-
At x=6: \frac{d^2y}{dx^2} = 12(6) - 42 = 72 - 42 = 30 > 0 (Local Minimum)
4. Calculate the minimum value at x=6:
Substitute x=6 into the original function:
