The 2th term of The A. P is 7 and 4th term is 28 Find The Common difference and The first term. help me please

d = 10.5, a₁ = - 3.5

Step-by-step explanation:

The n th term of an AP is

= a₁ + (n - 1)d

where a₁ is the first term and d the common difference

Given a₂ = 7 and a₄ = 28 , then

a₁ + d = 7 → (1)

a₁ + 3d = 28 → (2)

Subtract (1) from (2) term by term to eliminate a₁

2d = 21 ( divide both sides by 2 )

d = 10.5 ← common difference

Substitute d = 10.5 into (1)

a₁ + 10.5 = 7 ( subtract 10.5 from both sides )

a₁ = - 3.5 ← first term

step-by-step explanation:

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