ex1.计算。a x(x+15) Solution ar b d 5x(x+15)b-)+∞5x(x+15) b1 m b→>+∞515xx+15 lim Iunx-In(x+15)1k b→+∞15 b 5 2 lim=(In In) In 2 b→+∞15 b+152015. ( 15) 1. 5  + x x + dx ex 计算 Solution.   + = + + →+  b b x x dx x x dx 5 5 ( 15) lim ( 15) dx x x b b  + = − →+  5 ) 15 1 1 ( 15 1 lim b b x x 5 [ln ln( 15)] 15 1 = lim − + →+  ln 2 15 2 ) 20 5 ln 15 (ln 15 1 lim − = + = →+ b b b