Question

please answer these question ​

Answer 1

Answer:

a) 178

b) 1850

Step-by-step explanation:

A5 = A + 4d

A9 = A + 8d

66 - 38 = A + 8d - A - 4d

28 = 4d

d = 7

Putting d = 7 in A5

38 = A + 4(7)

38 = A + 28

A = 10

A25 = A + 24d

= 10 + 24(7)

= 10 + 168

= 178

S25 =

$\frac{n(a + an)}{2}$

$\frac{25(10 + 178)}{2}$

$\frac{25 \times 188}{2}$

$25 \times 74$

$1850$

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