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3 years ago

Let f(x) = x2 − 81. Find f−1(x).

1 answer:

3 0

F(x) = x² - 81

Finding f⁻¹(x) the inverse function

Let y = f(x) and solve for x.

y = x² - 81

y + 81 = x²

x² = y + 81

x = √(y + 81)

Recall f(x) = y, that means x = f⁻¹(y)

x = √(y + 81)

f⁻¹(y) = √(y + 81)

Therefore f⁻¹(x) = √(x + 81)

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You invested $19,000 in two accounts paying 4% and 8% annual interest, respectively.

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$10000 at 8%

Step-by-step explanation:

Let's assume that "x" is the amount deposited in the 4% account and "y" is the amount deposited in the 8% account.

Recall the formula for interest as : $I= P * R *t$

where I is the interest, R is the annual rate of interest and t is the number of years.

Since there are two investments, we need to add both interests at the end of the one year: I1 = x (0.04) (1) = 0.04 x and I2 = y (0.08) (1) = 0.08 y

Total Interest = Interest (from the 4% account) + Interest (from the 8% account)

Total Interest = $1160 = 0.04 x + 0.08 y

we also know that the total invested (x + y) adds to $19,000, that is:

$19,000 = x + y

Then we can solve these system of two equations by substitution, for example solving for y in the second equation and using the y substitution in the first equation;

y = 19000 - x

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Then the other investment was : y = $19000 - $9000 = $10000

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3 years ago