Which is a factor of x2-8x+15?

Question

Answer this

Answer 1

Best Answer - Chosen by Asker

(x - 5)(x - 3)

Asker's Rating:

Asker's Comment:

This is what i wanted and i ust wanted to let you know that i like the way that you answered this question cause i just needed the answer not how you got the answer

Answer 2

The question is likely: Factor x^2 - 8 x + 15.

1) You have a quadratic expression
the form of:
Ax^2 + Bx + C

2) You want to find the numbers p,q,r,s such that
Ax^2 + B x + C = (p x + q )( r x + s)

where the right hand side here is the factored form of
the original expression.

3) So multiply out (px + q)(rx + s)
p x + q
r x + s
_____________
(pr) x^2 + (rq + sp) x + qs

4) We compare this general form to the one they gave
you, so for your problem
p r =1
(rq + sp) =-8
qs = 15

5) A good guess would be to take p=r=1, so the second
term becomes
(q + p) = -8
Think about numbers that when multiplied together
give 15. These are:
(1)(15) = 15
(-1)(-15) = 15
(3)(5) = 15
(-3)(-5)=15

6) Remembering that p+q = -8
it looks like p=-3 and p=-5 will fit the bill.
So in factored form you have
(x - 3)(x - 5)

7) Check the answer
x - 3
x - 5
--------
x^2 - (3 + 5)x + 15
= x^2 - 8 x + 15

so, there you go.

Answer 3

Hi,

Good Question! Notice that the 15 here is from the product of two numbers when multiplied would give 15. Also, these two numbers when added together give us -8. Thinking about this, we need to recall the factors of 15 include: 1, 3, 5 and 15.

At this point, I'm sure you're thinking of the two factors -3 and -5 which is a very good observation!

Therefore we can say the following:

( x - 3 ) ( x - 5 ) <=== FINAL ANSWER

* NOTE: As a check, you can use the FOIL Method on this binomial to get the Quadratic Expression that you were originally presented with! =)

I hope that helps you out! Please let me know if you have any other questions!

Source(s):

College Calculus Student ; Math Tutor

Answer 4

Question Number 1 :
For this equation x^2 - 8*x + 15 = 0 , answer the following questions :
A. Calculate the Roots ( x1 and x2 ) !
B. Use factorization to find the root of the equation !

Answer Number 1 :
The equation x^2 - 8*x + 15 = 0 is already in a*x^2+b*x+c=0 form.
So we can imply that the value of a = 1, b = -8, c = 15.

1A. Calculate the Roots ( x1 and x2 ) !
Use abc formula and you get either
x1 = (-b+sqrt(b^2-4*a*c))/(2*a) or x2 = (-b-sqrt(b^2-4*a*c))/(2*a)
As we know that a = 1, b = -8 and c = 15,
we just need to subtitute the value of a,b and c in the abc formula.
Which produce x1 = (-(-8) + sqrt( (-8)^2 - 4 * (1)*(15)))/(2*1) and x2 = (-(-8) - sqrt( (-8)^2 - 4 * (1)*(15)))/(2*1)
Which is can be turned into x1 = ( 8 + sqrt( 64-60))/(2) and x2 = ( 8 - sqrt( 64-60))/(2)
Which is can be turned into x1 = ( 8 + sqrt( 4))/(2) and x2 = ( 8 - sqrt( 4))/(2)
So we get x1 = ( 8 + 2 )/(2) and x2 = ( 8 - 2 )/(2)
The answers are x1 = 5 and x2 = 3

1B. Use factorization to find the root of the equation !
x^2 - 8*x + 15 = 0
<=> ( x - 5 ) * ( x - 3 ) = 0
The answers are x1 = 5 and x2 = 3

Source(s):

This free Quadratic Solver should help you in the future :

http://orimath.blogspot.com/search/label…

Answer 5

Do you mean how to factor it? If that is what you mean, the answer is (x-5)(x-3)

Answer 6

x^2- 8x + 15
x^2 - 3x - 5x - 15
(x^2 - 3x) - (5x - 15)
x(x - 3) - 5(x - 3)
(x - 5)(x - 3)

Answer 7

x=3, x=5

Answer 8

ha i'm studying this 2...

Source(s):

me meme