题目

脱式计算。①32+6.4+68+3.6②10.27+0.4-8.27③18.51-9.03-0.97④64.3-18.75+15.7-11.25⑤7.41-(2.96+3.04)⑥4.28+2.08+3.62 答案：①32+6.4+68+3.6=（32+68）+（6.4+3.6）=100+10=110②10.27+0.4-8.27=10.27-8.27+0.4=2+0.4=2.4③18.51-9.03-0.97=18.51-（9.03+0.97）=18.51-10=8.51④64.3-18.75+15.7-11.25=（64.3+15.7）-（18.75+11.25）=80-30=50⑤7.41-(2.96+3.04)=7.41-6=1.41⑥4.28+2.08+3.62=4.28+3.62+2.08=7.9+2.08=9.98数列{an}的通项公式an＝－n2＋10n＋11，则该数列前________项的和最大．