SOLUTION: -the 4th term of an AP is 7 and the 9th term is 17 find the 15th term ?? -if 4 times the 4th term of an AP is equal to 7 times the 7th term,find its 11th term

Question 843458: -the 4th term of an AP is 7 and the 9th term is 17 find the 15th term ??
-if 4 times the 4th term of an AP is equal to 7 times the 7th term,find its 11th term

Found 2 solutions by TheInstructor, mathgenboy:
Answer by TheInstructor(29) (Show Source): You can put this solution on YOUR website!
Hey!
T4= a+3d =7 ----- (1)
T9= a+8d =17 ----- (2)
(2)-(1)
Therefore 5d = 10
d=2

a+ 6= 7
Therefore a = 1
T15= a+14d
T15 = 1 + 14(2) = 29

Answer by mathgenboy(3) (Show Source): You can put this solution on YOUR website!
The second question: Interpreting the question
AMP Parsing Error of [4*(a+ 3d)=7*(a+ 7d]: Invalid expression. Closing bracket expected at /home/ichudov/project_locations/algebra.com/templates/Algebra/Expression.pm line 187. .
collect like terms divide both sides by -3, then . Now substitute a=-10d, then . Therefore
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