Annika and April are working on the given problem.

Question

(x-4)(x+5)=0

 

Annika says that the answers are -4 and 5, while April says that the answers are 4 and -5. Who is correct and why?

 

Answer 1

(x-4)(x+5)=0

 

this can be expressed as 

 

x - 4 = 0 or x + 5 = 0

 

x = 4 or x = -5

Answer 2

(x-4)(x+5) = 0

 

By inspection, you can see that x = 4 makes the first factor equal to zero, hence the whole expression is zero.  Similarly, you can see that x = -5 makes the second factor zero, hence the whole expression equals zero.  The correct values of x are 4 and -5.  April is correct