Mathematics

Mathematics

Problem

The integrating factor of differential equation (x+2y3)dydx=2y(x + 2y^3) \frac{dy}{dx} = 2y is (A) ey22e^{\frac{y^2}{2}} (B) 1y\frac{1}{\sqrt{y}} (C) 1y2\frac{1}{y^2} (D) e−1y2e^{-\frac{1}{y^2}}
Intuitive explanation

This problem asks you to find an integrating factor—a function you multiply through to make a non-exact differential equation exact and solvable. First, rewrite the equation in standard form M dx+N dy=0M\,dx + N\,dy = 0 and check if it's exact by comparing partial derivatives. When it's not exact, look for an integrating factor that depends on only one variable (either xx or yy alone). The key is to compute 1N(∂M∂y−∂N∂x)\frac{1}{N}\left(\frac{\partial M}{\partial y} - \frac{\partial N}{\partial x}\right) and see if it depends only on yy—if so, your integrating factor has the form μ(y)=e∫(that expression) dy\mu(y) = e^{\int \text{(that expression)} \, dy}.

Intuitive explanation

This problem asks you to find an integrating factor—a function you multiply through to make a non-exact differential equation exact and solvable. First, rewrite the equation in standard form M dx+N dy=0M\,dx + N\,dy = 0 and check if it's exact by comparing partial derivatives. When it's not exact, look for an integrating factor that depends on only one variable (either xx or yy alone). The key is to compute 1N(∂M∂y−∂N∂x)\frac{1}{N}\left(\frac{\partial M}{\partial y} - \frac{\partial N}{\partial x}\right) and see if it depends only on yy—if so, your integrating factor has the form μ(y)=e∫(that expression) dy\mu(y) = e^{\int \text{(that expression)} \, dy}.

Browse the problem library