Question

Which of the following would best be solved using factoring by grouping?

1) x^2+3x- 10=0
2)3x^2+12x=8
3)x^2=25
4)x^3+ 5x^2- 9x- 45=0

Answer 1

The fourth

Explanation:

It has 4 terms

Answer 2

4)x^3+ 5x^2- 9x- 45=0

EXPLANATION

Factoring by grouping is used to factor expressions that have four terms.

Among the given options, the fourth option is

`x^3+ 5x^2- 9x- 45=0`

There are already four terms in this expression.

So we group the first two and the last two and factor.

We can see that x² is common to the first two terms and -5 is common to the last 2 terms.

The fourth choice is correct.