Q: If a3 = x+7 , a7 = x+49 . find a1 = ?
By Arithmetic Progression.
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answer is x=21
a=7
Step-by-step explanation:
a3=x+7
a+2d=x+7 (1)
a7=x+49
a+6d=x+49 (2)
subtract (1) from (2) , we get
4d=42
d=42/4=21/2
put d= in 1 equation
a+2(21/2)= x+7
a+21= x+7
a-x=7-21=-14
put d =21/2 in 2 equation
a+6(21/2)= x+49
a+63=x+49
a-x=49-63=-14
when we put d=21/2 in both equation we get a-x=-14.its means a=7 and x=21
because a-y=-14 and 7-21=-14
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