Engineering
Mathematics
Linear Differential Equation
Question
Column I Column II
(A) If f(x) = ∫0x2(cos1t+1)dt,x≥1 then the value of f "(x) is greater than or equal to (P) 1
(B) If H'(x) = (2x + 3) (x3 + x – 2)2 (x2 – 1) (x2 + 3x + 2) and ln g(x) = H(x) then number of local minimum of g(x) is less than or equal to (Q) 2
(C) The value of Limn → ∞14n(1+12+13+.....+19n) is greater than (R) 3
(D) If a conic satisfying the differential equation x2dy – dx = 2xy dx which passing through the point (1,−13)  has the eccentricity e then e2, is less than (S) 4
  (T) 6

 

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Solution

This is a matching question with four parts (A-D) and options (P-T). Each part requires solving a calculus or differential equation problem to find a numerical bound, then matching it to the correct option.

(A) Find f"(x) for f(x)=∫0x2(cos1t+1)dt. Use the Fundamental Theorem of Calculus and chain rule. f'(x)=2x(cos(1/|x|)+1). f"(x)≥2, so answer is (Q).

(B) Given H'(x) and ln g(x)=H(x), g'(x)/g(x)=H'(x). Find critical points from H'(x)=0. Number of local minima ≤3, so answer is (R).

(C) The limit is a Riemann sum: limn→∞1n∑k=19n1k. This approximates ∫091xdx=6. Value >4, so answer is (S).

(D) Solve the differential equation x²dy - dx = 2xydx. Rewrite as dy/dx = (2xy+1)/x². This is linear; integrating factor is 1/x². Solution is a hyperbola y = x - 1/(3x). Eccentricity e²=1+(b²/a²). For hyperbola y=x-1/(3x), e²<4, so answer is (R).

Final Answer: A→Q, B→R, C→S, D→R