A computer parts company wants to make a rectangular memory board that has a perimeter of 14 cm and a diagonal of length 5 cm. What are the dimensions of the​ board?

A computer parts company wants to make a rectangular memory board that has a perimeter of 28 centimeters and a diagonal length of 10 centimeters. Find the dimensions of the board. Consider the length to be the longer side.: Call the two sides L & W: the perimeter 2L + 2W = 28 Simplify, divide by 2 L + W = 14 L = (14-W); use this form for substitution

Step-by-step explanation:

Explanation:

x = width

y = length

both x and y are positive real numbers, and the units of which are in cm.

The perimeter of any rectangle is found by saying

P = 2*(length+width)

P = 2*(x+y)

Plugging in P = 14 leads us to

P = 2*(x+y)

14 = 2*(x+y)

14/2 = x+y

7 = x+y

Solve for one of the variables. Let's say we solve for y. That should get us y = 7-x which we'll use a bit later.

Notice how the diagonal forms two identical right triangles. The legs of which are x and y as defined earlier. The hypotenuse is 5, which is the diagonal length.

Use the pythagorean theorem to help solve for x

a^2 + b^2 = c^2

x^2 + y^2 = 5^2

x^2 + (7-x)^2 = 25 ... plug in y = 7-x

x^2 + 49 - 14x + x^2 = 25 ... use FOIL rule

2x^2-14x+49 = 25

2x^2-14x+49-25 = 0

2x^2-14x+24 = 0

2(x^2-7x+12) = 0

x^2-7x+12 = 0

(x-3)(x-4) = 0

x-3 = 0 or x-4 = 0

x = 3 or x = 4

If x = 3, then y = 7-x = 7-3 = 4

If x = 4, then y = 7-x = 7-4 = 3

We have this symmetry going on. If x is one of 3 or 4, then y is the other of those values. Because x = 3 and y = 4, or vice versa, this means we have a 3-4-5 right triangle (well to be fair we have two identical copies of such a triangle to form the rectangle).

Therefore, the dimensions of the rectangular board is 3 cm by 4 cm. The order doesn't matter so you could easily say "4 cm by 3 cm" to mean the same thing.

Check:

P = perimeter

P = 2*(length+width)

P = 2*(x+y)

P = 2*(3+4)

P = 2*7

P = 14

That helps confirm the answer.

answer: it's d

step-by-step explanation:

step-by-step explanation:

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