Question

Please Answer Correctly During Elimination Method Should We Make All Co-efficient Same...Please Explain Correctly
for ex. 1) a+9d=25
2)2a+4d=30

My Question is should i make 9d and 4d same co-efficient If Not Why ??​

Answer 1

Answer:

Hi mate,

Ur question is right.

We should make 9d and 4d same co-efficient because in elimination method,we can't eliminate 2 terms which are having two different co-efficients.We can also make 2a and a same co-efficients.This is because 2 terms should be eliminated in this method.Then we can do it perfectly.

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Answer 2

Step-by-step explanation:

Formula:-

nth term of AP, tn = a + (n-1) d  

Sum of n terms Sn = n/2[2a + (n-1)d]

a - first term and d = common difference

To find a and d

It is given that, a3=15 ,S10=125

We can write a + 2d = 15  ----(1)

10/2[2a + 9d ] = 125

⇒5[2a + 9d ] = 125

⇒2a + 9d = 25  ----(2)

(1)*2 ⇒ 2a + 4d = 30 ---(3)

(2) - (3) ⇒

5d = -5

d = -1

eq (1) ⇒ a + 2d = 15

a + -1*2 = 15

a = 15 + 2 = 17

To find a10

a10 = a + 9d = 17 + 9*-1 = 17 - 9 = 8

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