In Exercises 139-160, completely factor the expression. 140. 12x - 48 142. x - 9x 144. 2y3 - 7y2 - 15y 139. 6x - 54 141. x - 4x 143. 2x + 4x - 2x 145. 3x + x + 15x + 5 146. 13x + 6 + 5x 147. x + x - 8 148. x-x-16 149. x4 4x + x - 4x 150. 3u 2u+ 6 - u 151. (x + 1)2 - 4x 152. (x+8)2 - 36x 153. 213 16 154. 5x3 + 40 155. 4x(2x - 1) + (2x - 1) (156) 5(3-4x) - 8(34x)(5x - 1) 157. 7(3x + 2)2(1 x) + (3x + 2)(1-x) 158. 7x(2)(x + 1)(2x) - (x + 1)(7) 159 3(x - 2)(x + 1)4+ (x - 2)(4)(x + 1) 160. 5(x + 1)4(6x5)(3x + 2)3 + 3(3x + 2)(3)(x + 1)5