The differential equation
has characteristic equation
<em>r</em> ⁴ - <em>n </em>² <em>r</em> ² = <em>r</em> ² (<em>r</em> ² - <em>n </em>²) = <em>r</em> ² (<em>r</em> - <em>n</em>) (<em>r</em> + <em>n</em>) = 0
with roots <em>r</em> = 0 (multiplicity 2), <em>r</em> = -1, and <em>r</em> = 1, so the characteristic solution is
For the non-homogeneous equation, reduce the order by substituting <em>u(x)</em> = <em>y''(x)</em>, so that <em>u''(x)</em> is the 4th derivative of <em>y</em>, and
Solve for <em>u</em> by using the method of variation of parameters. Note that the characteristic equation now only admits the two exponential solutions found earlier; I denote them by <em>u₁ </em>and <em>u₂</em>. Now we look for a particular solution of the form
where
where <em>W</em> (<em>u₁</em>, <em>u₂</em>) is the Wronskian of <em>u₁ </em>and <em>u₂</em>. We have
and so
So we have
and hence
Finally, integrate both sides twice to solve for <em>y</em> :
Step-by-step explanation:
This is the second fundamental theorem of calculus.
d/dx ∫ₐᵇ f(x) dx = f(b) (db/dx) − f(a) (da/dx)
This is derived using chain rule:
d/dx g(f(x)) = g'(f(x)) f'(x)
Therefore:
d/dx ∫₀²ˣ arctan(t) dt = arctan(2x) (2x)' = 2 arctan(2x)
Answer:
y = -2x - 8
Step-by-step explanation:
Slope-intercept form is y = mx + b. Slope is m, and y-intercept is b. To do this, we substitute -2 for m and -8 for b. When we do this, we get y = -2x + -8. We can simplify this to y = -2x - 8.