a^2 – 5a – 20 factor completely

Question

anonymous · Answer

-5(4) right ?

vishweshshrimali5 · Answer

No not this time I think you have copied your question incorrectly
it should be 

a^2 - a - 20
right ?

anonymous · Answer

no it has 5 in this one

vishweshshrimali5 · Answer

ok

anonymous · Answer

i see it's prime so how do i show work

anonymous · Answer

is the answer
$$5+\sqrt{105}/2,5-\sqrt{105}/2$$

precal · Answer

when it is prime, we just state "prime" and do not attempt to factor.
Now if it said, solve then we solve using the quadratic formula

anonymous · Answer

7.623,-2.623

anonymous · Answer

yes or no?

anonymous · Answer

no because it's prime

anonymous · Answer

but it can be solved by discriminant method

anonymous · Answer

it just said factor and show work so i don't think i have to use that .

precal · Answer

correct, if the instructions were to factor write "prime"
if the instructions were to solve then use the quadratic formula

anonymous · Answer

It's prime!

Applying quadratic formula, we get:

a^2 – 5*a – 20 = 0

a = 1, b = - 5, c = - 20

b^2 - 4*a*c = 25 - 4*1*( - 20) = 105

a1 = ( - ( - 5) + sqrt(105))/2 = 5/2 + (1/2)*sqrt(105)

a2 = 5/2 - (1/2)*sqrt(105)

anonymous · Answer

ya??got it!