given a3 is 15 and s10 is 125, find d and a10
Answers
Step-by-step explanation:
Given:
a3=15
s10=125
d=?
a10=?
an=a+(n-1)d
a3=a+(3-1)d
15=a+2d
a+2d=15 _________ {1}
Sn=n/2(2a+{n-1}d)
S10=10/2(2a+{10-1}d)
125=5(2a+9d)
125/5=2a+9d
25=2a+9d ___________{2}
solving eq{1} & eq{2}
putting a value in eq {2}
2(15-2d)+9d=25
30-4d+9d=25
5d=25-30
=-5
【d=-1】
an=a+(n-1)d
a10=a+(10-1)d
a10=a+9d
a10=17+9(-1)
a10=17-9
【a10=8】
Answer:
an=a+(n-1)d
a3=a+(3-1)d
15=a+2d
a+2d=15 _________ {1}
Sn=n/2(2a+{n-1}d)
S10=10/2(2a+{10-1}d)
125=5(2a+9d)
125/5=2a+9d
25=2a+9d ___________{2}
solving eq{1} & eq{2}
putting a value in eq {2}
2(15-2d)+9d=25
30-4d+9d=25
5d=25-30
=-5
=d=-1
=>an=a+(n-1)d
a10=a+(10-1)d
a10=a+9d
a10=17+9(-1)
a10=17-9
a10=8