I can't seem to figure it out. Thanks!
How do you factor the expression -12a^2+20a-21
This expression can not be factorized in the set of real numbers.
There is formula for factorization of quadratic expression: ax^2+bx+c=a(x-x,)(x-x,,) , where x, and x.. are roots of quadratic equation ax^2+bx+c=0 . To find the roots we can use the formula x = (-b ± √D)/2a , where D=b^2-4ac . There are 2 roots if D>0 , there is 1root if D=0 , and zero roots in set of real numbers if D is negative.
Let's use information above: -12 a^2 + 20a - 21 = 0
D = 20^2 -4(-12)(-21) < 0