Question

d=5, s9=75 find a and a9​

Answer 1

Step-by-step explanation:

Sn = n/2{2a+(n-1)d}

s9=9/2{2a+(9-1)5}

75= 9/2{2a+40}

75= 9{2a+20}

75 = 9a+180

9a= 75-180

a= -105/9

= -35/3

a9 =-35/3+( 9-1 ) 5

= -35/3 +40

=(-35+120)/3

= 85/3

Answer 2

Answer:

s9= n/2+(2a+(n-1)d

75=9/2+(2a+(9-1)5

75=9/2+(2a+40)

75×2/9=2a+40

150/9 =2a+40

50/3=2a+40

50/3-40=2a

by taking LCM

50-120/3=2a

-70/3=2a

-70/3×2=a

-35/3=a

a9= a+8d

a9= -35/3+8×5

a9= -35/3+40

a9=-35+120/3. (by taking LCM)

a9= 85/3