Expression 3: Start sum from "i" equals 1 to "n" , end sum, StartFraction, left parenthesis, "b" minus "a" , right parenthesis Over "n" , EndFraction left parenthesis, 8 minus 1 half left parenthesis, "a" plus "i" times StartFraction, left parenthesis, "b" minus "a" , right parenthesis Over "n" , EndFraction , right parenthesis squared , right parenthesis equals 32n∑i=1b−an8−12a+i·b−an2