Friday, January 2, 2015

`y'-y = 16` Solve the first-order differential equation

`y' - y = 16`


To solve, rewrite the derivative as `dy/dx` .


`(dy)/dx - y = 16`


Then, express the equation in the form `N(y)dy = M(x) dx` .


`(dy)/dx = y+16`


`(dy)/(y+16) = dx`


Take the integral of both sides.


`int (dy)/(y+16) = int dx`


For the left side of the equation, apply the formula `int (du)/u = ln|u|+C` .


And for the right side, apply the formula `int adx =ax + C`.


`ln |y+ 16| + C_1 = x + C_2`


Then, isolate the y. To do so, move the C1 to the right side.


`ln|y+16| = x + C_2-C_1`


Since C1 and C2 represent any number, express it as a single constant C.


`ln|y+16| = x + C`


Then, convert this to exponential equation.


`y+16=e^(x+C)`


And, move the 16 to the right side.


`y = e^(x+C) - 16`



Therefore, the general solution is `y = e^(x+C)-16` .

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