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int4x cos(2-3x)dx

4xcos(23x)dx \int 4 x \cos (2-3 x) d x

Full solution

Q. 4xcos(23x)dx \int 4 x \cos (2-3 x) d x
  1. Set up integral: Let's start by setting up the integral we need to solve: 4xcos(23x)dx\int 4x \cos(2-3x)\,dx. We'll use a substitution method here. Let u=23xu = 2 - 3x, then du=3dxdu = -3 \,dx, or dx=du3dx = -\frac{du}{3}.
  2. Substitute uu and dxdx: Substitute uu and dxdx in the integral: (4xcos(u)(13)du)\int(4x \cos(u) * (-\frac{1}{3}) \,du). This simplifies to 43(xcos(u)du)-\frac{4}{3} \int(x \cos(u) \,du). Now, we need to express xx in terms of uu. From u=23xu = 2 - 3x, we solve for xx: dxdx00.
  3. Express xx in terms of uu: Plug xx back into the integral: 43(2u3cos(u)du)-\frac{4}{3} \int\left(\frac{2-u}{3} \cos(u) \,du\right). Simplify the constants: 49((2u)cos(u)du)-\frac{4}{9} \int((2-u) \cos(u) \,du). Now, we need to distribute the cos(u)\cos(u) inside the integral: 49((2cos(u)du)(ucos(u)du))-\frac{4}{9} \left(\int(2\cos(u) \,du) - \int(u \cos(u) \,du)\right).
  4. Distribute cos(u)\cos(u) inside integral: Solve the first integral (2cos(u)du)\int(2\cos(u) \, du). This is straightforward: 2sin(u)2\sin(u). For the second integral, (ucos(u)du)\int(u \cos(u) \, du), use integration by parts. Let v=uv = u, dv=cos(u)dudv = \cos(u) \, du, then du=dvdu = dv, and v=sin(u)v = \sin(u).