The solution of dy/dx = −4y with y(0) = 1 is

Answer and explanation

Correct answer: C. y = e^(−4x)

  1. Step 1: This is separable: dy/y = −4 dx, so ln y = −4x + C. Step 2. With y(0) = 1 the solution is y = e^(−4x). Answer: y = e^(−4x). Why not the others: y = e^(4x) is what you get if you get the sign of the exponent wrong. y = 1 − 4x is what you get if you assume a linear solution. y = e^(−x/4) is what you get if you invert the coefficient.

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