Question

find the four terms of an AP if the sum of first three terms is 12 and the sum of last three terms is 21

Answer 1

Answer:

4 terms are 1,4,7,10.

Step-by-step explanation:

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Answer 2

The four terms of an AP are 1, 4, 7, 10.

Step-by-step explanation:

Given:

• The sum of first three terms is 12
• The sum of last three terms is 21

Let the four terms of an AP are a-3d, a-d, a+d, a+3d.

$= > a - 3d + a - d + a + d = 12$

$= > 3a - 3d = 12$

$= > a - d = 4$

And,

$= > a - d + a + d + a + 3d = 21$

$= > 3a + 3d = 21$

$= > a + d = 7$

$= > a - d + a + d + a + 3d = 21$

$= > 4 + 7 + a + 3d= 21$

$= > a + 3d = 10$

So,

$= > a - 3d + a - d + a + d = 12$

$= > a - 3d + 4 + 7 = 12$

$= > a - 3d = 1$

The four terms of an AP are 1, 4, 7, 10.