Original formula =√3/2+3× 1-2-√3/2.

= 1

27.

∫x = sin 30 = 1/2

∴[ 1- 1/(x+3)]÷(x+4x+4)/(x-9)=(x+2)/(x+3)×(x+3)(x-3)/(x+2)=(x-3)/(x+2)=( 1/2-3)/( 1/2+2)=- 1

28. From 2(x+7)≤3x+3

x≥ 1 1

From x/3 < (x+ 1)/4+ 1.

x< 15

So the solution set of inequality is 1 1 < x < 15.