1=1.1+3=4=22.1+3+5=9=32,已知1+3+5+.+【2n-1】=225求整数n的值; 11+13+15+17+19+21+23+25=?= =缩了!是1=1.1+3=4=2².1+3+5=9=3²,已知1+3+5+.....+【2n-1】=225\(≧≦)==真的一个银都木有么QOQ
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1=1.1+3=4=22.1+3+5=9=32,已知1+3+5+.+【2n-1】=225求整数n的值; 11+13+15+17+19+21+23+25=?= =缩了!是1=1.1+3=4=2².1+3+5=9=3²,已知1+3+5+.....+【2n-1】=225\(≧≦)==真的一个银都木有么QOQ
1=1.1+3=4=22.1+3+5=9=32,已知1+3+5+.+【2n-1】=225求整数n的值; 11+13+15+17+19+21+23+25=?
= =缩了!是1=1.1+3=4=2².1+3+5=9=3²,已知1+3+5+.....+【2n-1】=225
\(≧≦)
==真的一个银都木有么QOQ
1=1.1+3=4=22.1+3+5=9=32,已知1+3+5+.+【2n-1】=225求整数n的值; 11+13+15+17+19+21+23+25=?= =缩了!是1=1.1+3=4=2².1+3+5=9=3²,已知1+3+5+.....+【2n-1】=225\(≧≦)==真的一个银都木有么QOQ
(1)根据规律可知,
1+3=[(1+3)/2]²=2²;
1+3+5=[(1+5)/2]²=3²;
1+3+5+…+(2n-1)={[1+(2n-1)]}²=n².
即:n²=225,则:n=15.
(2)11+13+15+17+…+25
=(1+3+5+…+25)-(1+3+5+…+9)
=[(1+25)/2]²-[(1+9)/2]²
=13²-5²
=144