The sum of4th and 6th term of an ap is 38 and sum of 5th and 10th teems is 58 find the ap
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the answer is in the pic
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Step-by-step explanation:
For an Ap let a be the first term and d be the common difference
according to the first condition
t4+t6 = 38
: . a + (4-1)d + a + (6-1)d = 38 ...[since tn= a+(n-1)d]
: . a+3d+a+5d=38
: . 2a+8d =38 ...(i)
according to second condition
t5+t10= 58
: . a + (5-1)d + a + (10-1)d = 58
: . a + 4d + a + 9d = 58
: . 2a + 13d = 58... (ii)
subtracting equation (i) from (ii) ,we get
2a + 13d = 58
2a + 8d = 38
- - -
5d = 20
: . d= 20/5
= 4
substituting d=4 in equation (i) we get
2a + 8d = 38
2a + 8(4)= 38
2a+ 32= 38
2a = 38-32
: . 2a = 6
: . a = 3
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