Question

In an AP, if d = –4, n = 7, an = 4, then a is


6

7

10

28

​

Answer 1

$\large{\underline{\sf{\blue{Given-}}}}$

• $\sf{d = - 4}$

• $\sf{n = 7}$

• $\sf{a_n = 4}$

$\large{\underline{\sf{\red{To \: Find-}}}}$

• $\sf{a = ?}$

$\large{\underline{\sf{\pink{Solution-}}}}$

$\boxed{\bf\green\star \: {a_n = a + (n - 1) \: d}}$

Placing Values,

$\sf\leadsto{4 = a + (7 - 1) \times ( - 4)}$

$\sf\leadsto{4 = a + (6) \times ( - 4)}$

$\sf\leadsto{4 = a - 24}$

$\sf\leadsto{4 + 24 = a}$

$\sf\star \: \underbrace\orange{a = 28} \: \star$

Hence,

• Value of a is 28.