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1. Dylan invested $47,000 in an account paying an interest rate of 4% compounded annually. Assuming no deposits or withdrawals are made, how long would it take, to the nearest tenth of a year, for the value of the account to reach $79,200?

2. x^2 + y^2 = 153 and y = -4x. If (x, y) is a solution to the system of equations above, what is the value of y^3?

Sagot :

zcathy

Answer:

(1) 13.0 years

(2) [tex]y^{3} =[/tex] {-1728, 1728}

Step-by-step explanation:

(1)

Compound annually:

[tex]Pe^{rt}[/tex] = A

(47000)[tex]e^{(0.04)(t)}[/tex] = 79200

[tex]e^{(0.04)(t)}[/tex] = [tex]\frac{79200}{47000}[/tex]

ln([tex]e^{(0.04)(t)}[/tex]) = ln([tex]\frac{79200}{47000}[/tex])

ln and e cancel out.

(0.04)(t) = ln([tex]\frac{79200}{47000}[/tex])

t = [tex]\frac{ln(\frac{79200}{47000})}{0.04}[/tex]

t = 13.0 years

(2)

[tex]x^{2} +y^{2} = 153\\y = -4x[/tex]

Substitute y with -4x.

[tex]x^{2} + (-4x)^{2} = 153[/tex]

Solve for x.

x = {-3, 3}

Plug in x values into any equation to find y.

y = -4(-3) and y = -4(3)

y = {-12, 12}

[tex]y^{3}[/tex] = [tex]-12^{3}[/tex] = -1728

[tex]y^{3}[/tex] = [tex]12^{3}[/tex] = 1728

Answer:

13.3    

Step-by-step explanation:

I got it right  

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