Question

Giải phương trình vi phân a. dy/dx b. y' + 2xy = 4x

Answer 1

Your first differential equation is incomplete, so I'll just look at the second one.

y' + 2xy = 4x

Multiply both sides by exp(x ²):

exp(x ²) y' + 2x exp(x ²) y = 4x exp(x ²)

The left side is the derivative of a product:

(exp(x ²) y )' = 4x exp(x ²)

Integrate both sides:

exp(x ²) y = ∫ 4x exp(x ²) dx

For the integral, substitute u = x ² and du = 2x dx :

exp(x ²) y = 2 ∫ exp(u) du

Solve for y :

exp(x ²) y = 2 exp(u) + C

exp(x ²) y = 2 exp(x ²) + C

y = 2 + C exp(-x ²)