Question 51431
If you have two numbers being multiplied together to produce 0, that means at least one of the numbers has to be 0 because 0 times anything else is always 0.  Therefore, that means that (x-4) must equate to a 0 thusly:  {{{x-4=0}}}.  Adding 4 to both sides produces:  {{{x-4+4=0+4}}}, which simplifies to {{{x=4}}}.  Because both factors are (x-4), there is only one answer; namely; x=4.