Question

Simplify this expression.

3x2(7x2 - 9)

A.
21x2 - 9
B.
21x2 - 27x2
C.
21x4 - 9
D.
21x4 - 27x2

Answer 1

Option D is correct.

Explanation:

In order to simplify the given expression we should know what Distributive property of number is.

It is given by a*x (b-c ) = axb -axc

that is if a is outside of the parenthesis then a is multiplied to all the term inside one by one

here in the question outside is
`3x^2` and inside is
`7x^2` and 9.

therefore
`3x^2` is multiplied to both
`7x^2` and 9

So first term is obtained by multiplying
`3x^2` by
`7x^2` which gives

`21x^4`

and second term is obtained by multiplying
`3x^2` by 9 we get

`27x^2`

So expression is
`21x^4`-
`27x^2`