Choose u and dv: Let's use integration by parts to solve the integral ∫4x2ln(−4x)dx. Integration by parts is given by ∫udv=uv−∫vdu, where we need to choose u and dv such that du and v are easily computable. Let's choose u=ln(−4x) and dv=4x2dx. Then we need to compute du and v.
Compute du: First, we compute du by differentiating u with respect to x. Since u=ln(−4x), dxdu=(−4x)1×(−4)=−x1. Therefore, du=−xdx.
Compute v: Next, we compute v by integrating dv. Since dv=4x2dx, v=∫4x2dx. To integrate x2, we use the power rule ∫xndx=x(n+1)/(n+1) for n=−1. Thus, v=4x3/3.
Apply integration by parts: Now we apply the integration by parts formula: ∫udv=uv−∫vdu. Substituting u, du, v, and dv, we get ∫4x2ln(−4x)dx=ln(−4x)⋅(34x3)−∫(34x3)⋅(−xdx).
Simplify the integral: Simplify the integral on the right: ∫(34x3)∗(−xdx)=−34∫x2dx. Again, we use the power rule for integration to find ∫x2dx=3x3.
Perform the integration: Perform the integration: −34∫x2dx=−34⋅(3x3)=−94x3.
Write down full expression: Now we have all the parts to write down the full expression for the integral: ∫4x2ln(−4x)dx=ln(−4x)⋅(34x3)−(−94x3).
Simplify the expression: Simplify the expression: ln(−4x)×(34x3)−(−94x3)=(34x3)ln(−4x)+94x3.
Add constant of integration: Finally, we add the constant of integration C to our result to get the indefinite integral: ∫4x2ln(−4x)dx=(34x3)ln(−4x)+94x3+C.
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