There was $800 deposited at 9% interest and $400 deposited at 4% interest.
The formula for simple interest is I = prt. Using our information we have:
88 = x(0.09)(1) + (1200-x)(0.04)(1)
88 = 0.09x + 48 - 0.04x
88 = 0.05x + 48
Subtract 48 from both sides:
88 - 48 = 0.05x + 48 - 48
40 = 0.05x
Divide both sides by 0.05:
40/0.05 = 0.05x/0.05
x = 800
1200 - x = 400
The solution of <span>0 = x2 − 5x − 36 is x = - 4 and x = 9
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