Normal
4]u1-(u1+2d)+u1+4d=65 u1+u1+6d=325giai he phuong trinh duoc u1=-130;d=97.56]a3=11;a6=23 thi a3=a1+2d=11a6=a1+5d=23 giai duoc a1=3;d=47]a1+2d+a1+9d=24(a1+d)**+(a1+4d)**+90giai ra d=2;a1=1va d=4.4;a1=-12.2 ** đó là bình phương
4]u1-(u1+2d)+u1+4d=65
u1+u1+6d=325
giai he phuong trinh duoc u1=-130;d=97.5
6]a3=11;a6=23 thi a3=a1+2d=11
a6=a1+5d=23 giai duoc a1=3;d=4
7]a1+2d+a1+9d=24
(a1+d)**+(a1+4d)**+90
giai ra d=2;a1=1va d=4.4;a1=-12.2 ** đó là bình phương
