Question

Given a square with side lengths represented by the function f(x)=2x+5, find the square.

A. 2x^2+10x+25
B. 4x^2+20x+25
C. 4x^2+20x+10
D. 2x^2+5x+10

Answer 1

`B. 4x^2+20x+25`

Explanation:

The length of the side:

`2x+5`

In a square all sides have the same length.

And the area of a square is given by the formula:

`Area=(length)^2`

so, substituting that the length is
`2x+5`

`Area=(2x+5)^2`

and we solve this squared binomial with the formula:

`(a+b)^2=a^2+2ab+b^2`

in this case
`a=2x` and
`b=5`

thus, we get:

`Area= (2x)^2+2(2x)(5)+(5)^2`

and solving:

`Area=4x^2+20x+25`

which is option B.