Question

Solve the following equation by graphing the related function.

1. 4x^2 + 8x = 32

A: ?

Use the Zero Product Property to solve the following equation.

2. x(x + 3) = 32

A: ?

3. Solve 3x^2 + 5 = 21. Round to the nearest hundredth.

A: x = 5.33
x = 5.0 or 5?

Answer 1

1.

4x^2 + 8x = 32
4x^2 + 8x - 32 = 0
x^2 + 2x - 8 = 0

let y = x^2 + 2x - 8
now graph this, and look at where it crosses the x-axis.
From Wolfram's graph
http://www.wolframalpha.com/input/?i=y+%3D+x%5E2+%2B+2x+-+8

we can see x = -4 or x = 2

2.

x(x + 3) = 32
x^2 + 3x - 32 = 0
This does not factor over the rationals.
Since it asked to use the "zero product property" I was expecting it to factor. Is there a typo
(the fact that both #1 and #2 have 32 on the right side, might suggest a typo)

3.

3x^2 + 5 = 21
3x^2 = 16
x^2 = 16/3
x = ± 4/√3 = appr ± 2.31

Again, I suspect a typo, since your solution of x = 5.33 doesn't even come close as a solution