Question

A new office building in town has x2 + 4 floors. Each floor is 3x2 – 5 feet high. Which expression shows the total height of this office building?

A. 3x4 – 20 feet
B. 3x4 + 7x2 – 20 feet
C.4x2 – 1 feet
D. 4x4 + 6x2 – 20 feet

Answer 1

answer : B

Explanation:

Answer 2

Answer: OPTION B.

Explanation:

You know that:

• 
  `x^(2)+4` represents the number of floors of the new office building in town.

• 
  `3x^(2)-5` represents the height of each floor in feet.

Therefore, you must multiply
`x^(2)+4` by
`3x^(2)-5` to obtain the expression that shows the total height in feet of this office building.

Then:

`(x^(2)+4)(3x^(2)-5)=3x^4-5x^2+12x^2-20`

Add the like terms:

`=3x^4+7x^2-20`

Therefore, the answer is the option B.