Original investment of $17,000 at two interest rates. Rate one interest after 1 year is I(x) = -.005x +425, where x is interest at 2.0%. Rate two is at 2.5% and the total interest for both is $409. What is interest earned for both certificates?

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Given

I(x)=409 (i)

But

I(x)=-.005x+425 (ii)

From (i) and (ii), we have

409=-.005x+425

.005x=425-409

.005x=16

x=16/(.005)

x=3200

Thus

$3200 invested at rate of 2.0% and $13800 invested at rate of 2.5% .

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