Question

a3==15,s10=125,d=?and a10= ?​

Answer 1

125 = (2a + 9d )5

2a + 9d = 25 ---------1

and also, (15 = a + 2d) × 2

• 30 = 2a + 4d --------------2
• now, subtract 1-2

we get 5d =-5

• d= -1

putting in 1 we get

, a = 17

so a10 = a+ 9d

• 17 +9(-1)
• 8

hope it helps you

Answer 2

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