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Interest in mathematical problems (involving a quadratic equation) (middle school)
Solution: let the annual interest rate of the first deposit be x,

According to the meaning of the question, [100 (1+x)-50] (1+x) = 63.

50x2+ 125x- 13 = 0。

The result is x 1 =, x2 =-.

∫x2 =- irrelevant,

∴x= = 10%。

A: The annual interest rate for the first deposit is 10%.

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