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Factor x^2 - x - 40

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2 Answers

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.
 
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