Simple differential equation problem

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SUMMARY

The discussion focuses on solving the differential equation dy/dx = 4x - 2y by finding constants a and b in the linear equation y = ax + b. The solution process reveals that for the equation to hold for all x, the condition 4 - 2a = 0 must be satisfied, leading to a = 2 and b = -1. The relationship a = -2b is established, indicating that once a is chosen, b can be directly determined. This analysis provides a clear method for solving similar linear differential equations.

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NihalRi
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Homework Statement


Find constants a and b such that y=ax + b is a solution to the differential equation
dy/dx = 4x - 2y

Homework Equations

The Attempt at a Solution


I already have the solution that is:
a=4x-2 (ax+b) (I'm fine with this part)
a = (4-2a) x - 2b (what happened here?)

4-2a=0 (why?) a= -2b (why?)
a= 2
b=-1
 
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NihalRi said:
a = (4-2a) x - 2b (what happened here?)
##
a=4x-2 (ax+b) \Leftrightarrow a=4x-2ax-2 b \Leftrightarrow a= (4-2a) x-2 b ## can only be true for all x if ##(4-2a)=0##. What remains is ## a = -2b ## . Pick an a and a b follows.
 
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BvU said:
##
a=4x-2 (ax+b) \Leftrightarrow a=4x-2ax-2 b \Leftrightarrow a= (4-2a) x-2 b ## can only be true for all x if ##(4-2a)=0##. What remains is ## a = -2b ## . Pick an a and a b follows.

Thank you
 

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