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Engineering Mathematics Miscellaneous

Engineering Mathematics

  1. Consider the following differential equation :
    dy
    = -5y ; initial condition; y = 2 at t = 0 The value of y at t = 3 is
    dt

    1. -5e-10
    2. 2e-10
    3. 2e-15
    4. -15e2
Correct Option: C

dy
= -5y
dt

dy
= -5dt
y

By Integrating above equation, we get
ln y = 5t + c
at t = 0 , y = 2
ln 2 = c
So, ln y = – 5t + ln 2
ln
y
= -5t
2

y
= e-5t
2

y = 2e-5t
at t = 3
y = 2 e-15



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