3. Use the method of substitution to find the following indefinite integrals a ) ] -3 (2x+ 7)3 dx b ) [ 8e 4 x 2 dx c) [15x*(x' + 3) 'dx d) ] 6.x- +2 -dx e) xv2x-Idx x'+x+5 X (x -5)3 dx