来自顾国彪的问题
1.已知a4=4,a9=972,求an2.等比数列{an}中,已知a1+a2+a3=-3,a1a2a3=8,求a4
1.已知a4=4,a9=972,求an
2.等比数列{an}中,已知a1+a2+a3=-3,a1a2a3=8,求a4
1回答
2020-04-11 21:29
1.已知a4=4,a9=972,求an2.等比数列{an}中,已知a1+a2+a3=-3,a1a2a3=8,求a4
1.已知a4=4,a9=972,求an
2.等比数列{an}中,已知a1+a2+a3=-3,a1a2a3=8,求a4
1a9/a4=q^5=243所以q=3则an=4*3^n-4
2由a1a2a3=8可知a2=2所以2/q+2+2*q=-3则q=-0.5或者-2所以a4=0.5或者8