Question

A photographer needs a frame for an 5 x 7 inch picture, such that the total area is 80 in? Calculate the width of

the frame. Which of the following quadratic equations would be used when solving this?
4x^2 + 24x = 45
4x^2 + 12x = 45
2x^2 + 24 = 45
2x^2 + 12x = 45

Answer 1

The answer is 4x^2+24x=45

Explanation:

I got it right on my test.

Answer 2

4·x² + 24·x = 45

Explanation:

The total area of the frame and picture needed by the photographer = 80 in²

The size of the picture that will be in the frame = 5 × 7 inch

The length of the picture = 7 inches

The width of the picture = 5 inches

Let x represent the width of the frame, we get;

The width of the total area = The width of the picture + 2 × The width of the frame

Therefore, the width of the total area = 5 + 2·x

The length of the total area = The length of the picture + 2 × The width of the frame

Therefore, the length of the total area = 7 + 2·x

We get;

The total area = Total length × Total width

∴ The total area = (5 + 2·x) × (7 + 2·x)

We are given that the total area = 80, therefore, by transitive property of equality, we have;

(5 + 2·x) × (7 + 2·x) = 80

35 + 10·x + 14·x + 4·x² = 80

4·x² + 24·x = 80 - 35 = 45

∴ 4·x² + 24·x = 45

Therefore, the quadratic equation that can be used in solving for the width is 4·x² + 24·x = 45.