Question

解方程组：a+aq3=18 aq2+aq=12求过程!

Answer 1

a+aq^3=18·······················1

aq^2+aq=12····················2

1式比2式得：

(1+q^3)/q(q+1)=3/2

(1+q)(q^2-q+1)/q(q+1)=3/2

(q^2-q+1)/q=3/2

2q^2-5q+2=0

(2q-1)(q-2)=0

解得：q=1/2 或 q=2

当q=1/2时代入1式得：a+a/8=18 解得：a=16

当q=2时代入1式得：a+8a=18 解得：a=2