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.