Identify integral: Identify the integral that needs to be solved.We need to find the indefinite integral of the function −4x2e4x with respect to x.
Use integration by parts: Use integration by parts.Integration by parts formula is ∫udv=uv−∫vdu.Let u=x2 (which implies du=2xdx) and dv=−4e4xdx (which implies v=−e4x).
Differentiate and integrate: Differentiate u and integrate dv. Differentiating u gives us du=2xdx. Integrating dv gives us v=−4e4x.
Apply integration by parts: Apply the integration by parts formula.∫−4x2e4xdx=uv−∫vdu= x2(−e4x/4)−∫(−e4x/4)(2xdx)= −x2e4x/4+(1/2)∫xe4xdx
Apply integration by parts again: Apply integration by parts again to the remaining integral.For the integral ∫xe4xdx, let u=x (which implies du=dx) and dv=e4xdx (which implies v=4e4x).
Differentiate and integrate: Differentiate u and integrate dv for the second application of integration by parts.Differentiating u gives us du=dx.Integrating dv gives us v=4e4x.
Apply integration by parts: Apply the integration by parts formula to the remaining integral.∫xe4xdx=uv−∫vdu= x(4e4x)−∫(4e4x)dx= x(4e4x)−(16e4x)+C
Substitute and simplify: Substitute the result from Step 7 back into the equation from Step 4.−4x2e4x+21(x(4e4x)−16e4x+C)=−4x2e4x+8x(e4x)−32e4x+2C
Substitute and simplify: Substitute the result from Step 7 back into the equation from Step 4.−4x2e4x+21(4x(e4x)−16e4x+C)= −4x2e4x+8x(e4x)−32e4x+2CCombine the constants and simplify the expression.The final answer is the indefinite integral of the given function:∫−4x2e4xdx=−4x2e4x+8x(e4x)−32e4x+C
More problems from Evaluate definite integrals using the chain rule