Introduction
To solve a differential equation of the form 2y'' - 4y' - 3y 0, we
first need to rewrite it in standard form. This allows us to identify the
characteristic equation which we can solve to find the roots that dictate the
general solution.
Revisiting the Standard Form of the Differential Equation
Starting with the given differential equation:
2y'' - 4y' - 3y 0, we can rewrite it as:
y'' - 2y' - frac{3}{2} y 0.
Identification of the Characteristic Equation
The method involves assuming a solution of the form y e^{rt}. By
substituting y e^{rt} into the differential equation, we obtain the
characteristic equation:
r^2 - 2r - frac{3}{2} 0.
Solving the Characteristic Equation
Using the quadratic formula r frac{-b pm sqrt{b^2 - 4ac}}{2a}, where
a 1, b -2, c -frac{3}{2}, we can solve for r.
r frac{-(-2) pm sqrt{(-2)^2 - 4 cdot 1 cdot (-frac{3}{2})}}{2 cdot 1}
frac{2 pm sqrt{4 6}}{2}
frac{2 pm sqrt{10}}{2}
1 pm frac{sqrt{10}}{2}.
The General Solution with Complex Roots
For second-order linear differential equations with complex roots of the
form r alpha pm beta i, the general solution is given by:
y(t) e^{alpha t}(C_1 cos(beta t) C_2 sin(beta t)), where C_1 and C_2 are constants.
Given alpha -1 and beta frac{sqrt{2}}{2}, the general solution is:
y(t) e^{-t}(C_1 cos(frac{sqrt{2}}{2} t) C_2 sin(frac{sqrt{2}}{2} t)).
Alternative Solution Using Euler's Identity
Another approach involves assuming a solution proportional to
y(x) e^{lambda x}. By substituting y e^{lambda x}, we obtain:
2 lambda^2 - 4lambda - 3 0. Solving this quadratic equation, we get:
lambda -1 pm ifrac{sqrt{2}}{2}.
The general solution is then:
y(x) c_1 e^{-x} cos(frac{sqrt{2}}{2} x) c_2 e^{-x} sin(frac{sqrt{2}}{2} x).
Conclusion
The general solution of the given differential equation is a combination of
exponential and trigonometric functions, which helps describe the behavior
of the system under consideration. This method can be applied to a wide range
of linear differential equations with constant coefficients.