Question

solve
x^2 + x - 12 = 0
quadratic formula??

Answer 1

to do this you can either just factor it out (if it is factorable) or use quadratic formula.

since it's factorable,
(x + 4)(x - 3) = 0, thus
x = -4 and x = 3

using quadratic formula:
x = [-b +- sqrt(b^2 - 4ac)]/(2a)
where
a = numerical coefficient of x^2
b = numerical coefficient of x
c = constant
substituting,
x = [-1 +- sqrt(1^2 - 4(1)(-12))]/(2*1)
x = [-1 +- sqrt(1 + 48)]/2
x = [-1 +- sqrt(49)]/2
x = [-1 +- 7]/2
there are two answers. we split the operation to plus and minus:
x = (-1 + 7)/2
x = 6/2
x = 3 (first root)

x = (-1 - 7)/2
x = -8/2
x = -4 (second root)

hope this helps~ :)