The solutions to the given differential equations are:
y = x³ + 7y = 3e^(-2x)y₁ = cos(2x), y₂ = sin(2x)y₁ = e^(3x), y₂ = e^(-3x)y = e^x - e^(-x)y₁ = e^(-2x), y₂ = xe^(-2x)y₁ = e^x cos(x), y₂ = e^x sin(x)y₁ = cos(x) - cos(2x), y₂ = sin(x) - cos(2x)y = 1 + x²y₁ = x - ln(x), y₂ = -1 - ln(x)y₁ = x², y₂ = x^(-2)y₁ = xcos(ln(x)), y₂ = xsin(ln(x))
To verify that each given function is a solution of the given differential equation, we will substitute the function into the differential equation and check if it satisfies the equation.
1. y' = 3x²; y = x³ + 7
Substituting y into the equation:
y' = 3(x³ + 7) = 3x³ + 21
The derivative of y is indeed equal to 3x², so y = x³ + 7 is a solution.
2. y' + 2y = 0; y = 3e^(-2x)
Substituting y into the equation:
y' + 2y = -6e^(-2x) + 2(3e^(-2x)) = -6e^(-2x) + 6e^(-2x) = 0
The equation is satisfied, so y = 3e^(-2x) is a solution.
3. y" + 4y = 0; y₁ = cos(2x), y₂ = sin(2x)
Taking the second derivative of y₁ and substituting into the equation:
y"₁ + 4y₁ = -4cos(2x) + 4cos(2x) = 0
The equation is satisfied for y₁.
Taking the second derivative of y₂ and substituting into the equation:
y"₂ + 4y₂ = -4sin(2x) - 4sin(2x) = -8sin(2x)
The equation is not satisfied for y₂, so y₂ = sin(2x) is not a solution.
4. y" = 9y; y₁ = e^(3x), y₂ = e^(-3x)
Taking the second derivative of y₁ and substituting into the equation:
y"₁ = 9e^(3x)
9e^(3x) = 9e^(3x)
The equation is satisfied for y₁.
Taking the second derivative of y₂ and substituting into the equation:
y"₂ = 9e^(-3x)
9e^(-3x) = 9e^(-3x)
The equation is satisfied for y₂.
5. y' = y + 2e^(-x); y = e^x - e^(-x)
Substituting y into the equation:
y' = e^x - e^(-x) + 2e^(-x) = e^x + e^(-x)
The equation is satisfied, so y = e^x - e^(-x) is a solution.
6. y" + 4y^2 + 4y = 0; y₁ = e^(-2x), y₂ = xe^(-2x)
Taking the second derivative of y₁ and substituting into the equation:
y"₁ + 4(y₁)^2 + 4y₁ = 4e^(-4x) + 4e^(-4x) + 4e^(-2x) = 8e^(-2x) + 4e^(-2x) = 12e^(-2x)
The equation is not satisfied for y₁, so y₁ = e^(-2x) is not a solution.
Taking the second derivative of y₂ and substituting into the equation:
y"₂ + 4(y₂)^2 + 4y₂ = 2e^(-2x) + 4(xe^(-2x))^2 + 4xe^(-2x) = 2e^(-2x) + 4x^2e^(-4x) + 4xe^(-2x)
The equation is not satisfied for y₂, so y₂ = xe^(-2x) is not a solution.
7. y" - 2y + 2y = 0; y₁ = e^x cos(x), y₂ = e^x sin(x)
Taking the second derivative of y₁ and substituting into the equation:
y"₁ - 2(y₁) + 2y₁ = e^x(-cos(x) - 2cos(x) + 2cos(x)) = 0
The equation is satisfied for y₁.
Taking the second derivative of y₂ and substituting into the equation:
y"₂ - 2(y₂) + 2y₂ = e^x(-sin(x) - 2sin(x) + 2sin(x)) = 0
The equation is satisfied for y₂.
8. y" + y = 3cos(2x); y₁ = cos(x) - cos(2x), y₂ = sin(x) - cos(2x)
Taking the second derivative of y₁ and substituting into the equation:
y"₁ + y₁ = -cos(x) + 2cos(2x) + cos(x) - cos(2x) = cos(x)
The equation is not satisfied for y₁, so y₁ = cos(x) - cos(2x) is not a solution.
Taking the second derivative of y₂ and substituting into the equation:
y"₂ + y₂ = -sin(x) + 2sin(2x) + sin(x) - cos(2x) = sin(x) + 2sin(2x) - cos(2x)
The equation is not satisfied for y₂, so y₂ = sin(x) - cos(2x) is not a solution.
9. y' + 2xy² = 0; y = 1 + x²
Substituting y into the equation:
y' + 2x(1 + x²) = 2x³ + 2x = 2x(x² + 1)
The equation is satisfied, so y = 1 + x² is a solution.
10 x²y" + xy' - y = ln(x); y₁ = x - ln(x), y₂ = -1 - ln(x)
Taking the second derivative of y₁ and substituting into the equation:
x²y"₁ + xy'₁ - y₁ = x²(0) + x(1) - (x - ln(x)) = x
The equation is satisfied for y₁.
Taking the second derivative of y₂ and substituting into the equation:
x²y"₂ + xy'₂ - y₂ = x²(0) + x(-1/x) - (-1 - ln(x)) = 1 + ln(x)
The equation is not satisfied for y₂, so y₂ = -1 - ln(x) is not a solution.
11. x²y" + 5xy' + 4y = 0; y₁ = x², y₂ = x^(-2)
Taking the second derivative of y₁ and substituting into the equation:
x²y"₁ + 5xy'₁ + 4y₁ = x²(0) + 5x(2x) + 4x² = 14x³
The equation is not satisfied for y₁, so y₁ = x² is not a solution.
Taking the second derivative of y₂ and substituting into the equation:
x²y"₂ + 5xy'₂ + 4y₂ = x²(4/x²) + 5x(-2/x³) + 4(x^(-2)) = 4 + (-10/x) + 4(x^(-2))
The equation is not satisfied for y₂, so y₂ = x^(-2) is not a solution.
12. x²y" - xy' + 2y = 0; y₁ = xcos(ln(x)), y₂ = xsin(ln(x))
Taking the second derivative of y₁ and substituting into the equation:
x²y"₁ - xy'₁ + 2y₁ = x²(0) - x(-sin(ln(x))/x) + 2xcos(ln(x)) = x(sin(ln(x)) + 2cos(ln(x)))
The equation is satisfied for y₁.
Taking the second derivative of y₂ and substituting into the equation:
x²y"₂ - xy'₂ + 2y₂ = x²(0) - x(cos(ln(x))/x) + 2xsin(ln(x)) = x(sin(ln(x)) + 2cos(ln(x)))
The equation is satisfied for y₂.
Therefore, the solutions to the given differential equations are:
y = x³ + 7
y = 3e^(-2x)
y₁ = cos(2x)
y₁ = e^(3x), y₂ = e^(-3x)
y = e^x - e^(-x)
y₁ = e^(-2x)
y₁ = e^x cos(x), y₂ = e^x sin(x)
y = 1 + x²
y₁ = xcos(ln(x)), y₂ = xsin(ln(x))
Learn more about differential equation
https://brainly.com/question/32538700
#SPJ11
