The problem
Hello
FACTORING EQUATION QUESTION .
EQUATION IS -r^2 +r +30
I know that when grouping equations in this particular format ,
that the sum of the factors of the last number ( 30) is suppose to equal the middle number ( r) .
However , In the math calculator , it split the middle number into 6r +5r ...
So , my question is, seeing how you don't know what the middle number ( r) is ,
why split it into 6r +5r ? why not 10r +3r ? or 2r + 15r ?
Thank you
Answer provided by our tutors
First the equation is a little different because you typically don't want the quadratic term to be negative, so you multiply the whole equation by -1:
r^2 -r -30 = 0
I will rewrite this to make the process more obvious:
r^2 -1*r -30 = 0
The question we are asking now which two numbers will give you -30 when multiplied and -1 when added. The only answer to this 'puzzle' is -6 and 5 -- so there are two conditions to consider, not just one.
REgards
NJ