Ryan S. answered • 03/17/20

Computer Science student and Researcher With a minor in Mathematics

x^2 - 4x - 21

can be factored as:

(x-7)(x+3)

Giving us the zero's/roots/INTERCEPTS of x. *These points are where the graph crosses the X axis.

given this,

y = (x-7)(x+3)

is our intercept form.

TIPS:

the best way to factor is to look at the two values on the right (in this example: -4 and -21)

and look at the factors of 21: (1*21) , (3*7)

we know since 21 is negative, one of these numbers must be negative, so which of the factors added together- keeping in mind that one must be negative - will add up to -4? This is the best way to factor when x^2 does not have a constant in front.