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# Factor x^2 - x - 40

I need help with this please

### 2 Answers by Expert Tutors

Jason S. | My goal is the success of my students. Knowledge-Patience-HonestyMy goal is the success of my students. K...
4.9 4.9 (115 lesson ratings) (115)
1
This expression does not factor.

The factors of 40 are 1 and 40, 2 and 20, 4 and 10, and 5 and 8.

Since the last term is -40, one of the factors must be positive and one must be negative.

|40-1| = 39
|20-2| = 18
|10-4| = 6
|5-8| = 3

Since none of those = -1, the express is "prime" and can't be factored.

Wendy B. | Math, Sciences, and General Education InstructorMath, Sciences, and General Education In...
5.0 5.0 (17 lesson ratings) (17)
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Hi,
To factor x^2 - x - 40, you have to put it into a quadratic formula and solve it that way.
1.  x^2 - x - 40 = 0 :  quadratic formula = x =[ -b + - (square root of b^2 - 4ac)] all divided by 2a.
2.  In this case: a = 1; b = -1; c = -40
so: x = [-(-1) + - (square root of (-1)^2 - 4(1)(-40)] divided by 2(1).
3.  x=[1 + - (square root of (1 + 160)] divided by 2
4. x = [1 + - (square root of 161)] divided by 2