SOLUTION: Hello, Sorry to bother you again but I can seem to grasp the following to put into an equation. It from Practical Application of Quadratic Equations Solve the questions A bu

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Question 152894: Hello,
Sorry to bother you again but I can seem to grasp the following to put into an equation. It from Practical Application of Quadratic Equations Solve the questions
A business invests $10,000 in a savings account for two years. At the beginning of the second year, an additional $3500 is invested. At the end of the second year, the account balance is $15,569.75. What was the annual interest rate?
Thank you,
Craig
Answer by scott8148(6628) About Me  (Show Source):
You can put this solution on YOUR website!
end of 1st yr __ 10000(1+r)

end of 2nd yr __ [10000(1+r)+3500](1+r)=15569.75

10000+10000r+3500+10000r+10000r^2+3500r=15569.75 __ subtracting 15569.75 __ 10000r^2+23500r-2069.75=0

use quadratic formula to find r


r=8.5%