Engineering
Mathematics
Introduction to Area
Question

Let f : [0, ∞) → R be a continuous function such that f(x) = 1 – 2x +∫0xex−tf(t) dt for all x ∈ [0, ∞). Then, which of the following statement(s) is(are) TRUE?

The curve y = f(x) passes through the point (1, 2).

The area of the region {  (x,y)∈[0, 1]×R:f(x)≤y≤1−x2  } is .π–24

The area of the region {  (x,y)∈[0, 1]×R:f(x)≤y≤1−x2  } is π−14.

The curve y = f(x) passes through the point (2, – 1).

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Solution

 f (x) = 1 – 2x + ex∫0xe−t⋅f(t) dt

 f '(x) = – 2 + ex∫0xe−t⋅f(t) ⋅dt+ex⋅e−x⋅f(x)

 dydx = – 2 + (y + 2x – 1) + y

 dydx – 2y = 2x – 3

y×e–2x=∫e−2x (2x−3) dx

y×e–2x=e−2x−2 (2x−3)+∫e−2x ⋅dx

=e−2x−2 (2x−3)−e−2x2+C

2y = – (2x – 3) – 1 + (2c) × e2x      (∵  f (0) = 1, then c = 0)

y = – x + 1

 

Ar =π4−12