how do you factor m^2-3m-4

Question

T

Answer 1

m² - 3m - 4 = (m + a)(m + b)

 

Find 2 numbers a and b such that

a + b = -3

ab = -4

 

Usually, just try guessing.  Note that

 

a = 1

b = -4 

 

works.  Then

 

m² - 3m - 4 = (m + 1)(m - 4)

 

Expand (m + 1)(m - 4) to test the solution.