Question

Whats the factoring of a^2-6a-21=-5 ?

Answer 1

So before we can factor this equation, we first have to set the equation to zero. To do this, add 5 on both sides of the equation:

`a^2-6a-16=0`

Next, I am going to be factoring by grouping. Firstly, what two terms have a product of -16a² and a sum of -6a? That would be -8a and 2a. Replace -6a with 2a - 8a:

`a^2+2a-8a-16=0`

Next, a² + 2a and -8a - 16 separately. Make sure that they have the same quantity on the inside of the parentheses:

`a(a+2)-8(a+2)=0`

Now you can rewrite this equation as
`(a-8)(a+2)=0` , which is your final answer.