the sum of seventh and eighth term of AP is 4 x + 7 and the 11 term is 2 x + 5 find the first and the common difference of ap for x is equal to 1
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Step-by-step explanation:
seventh term= a+6d
eighth term=a+7d
a+6d+a+7d = 4x +7
2a+13d=4x+7
given x=1
2a+ 13d=11
a=11-13d/2
eleventh term = 2x+5
a+10d=7
11-13d/2+10d=7
11-13d+20d=14
11+7d=14
7d=3
d=3/7
a=11-13(3/7)/2
=11-39/14
=154-39/14
=115/9
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