Sn=75000 a=1500 d=500 find n
Answers
Answered by
2
Step-by-step explanation:
Sn=75000
a=1500
d=500
to find n
required formula Sn=n/2[2a+(n-1)d]
75000=n/2[2(1500)+(n-1)500]
75000×2=n[3000+500n-500]
150000=n[500n+2500]
500n²+2500n-150000=0
n²+5n-300=0
n²+20n-15n-300=0
n(n+5)-15(n+5)=0
n-15=0,n+5=0
n=15,n=-5
n=15,-5
Similar questions