
Patrick B. answered 02/25/21
Math and computer tutor/teacher
y = x(x+2)(x-3)
the solutions are x=0, x=-2, x=3
so the X-intercepts, roots, zeros, are (0,0), (2,0), (3,0)
the y-intercept is ALSO (0,0) becuase y=0 when x=0
so (0,0) serves double duty as BOTH the y-intercept and an x-intercept
SORTS the solutions: -2, 0 , 3
There are 4 intervals if interest:
(-infinity,-2)
(-2,0)
( 0,3 )
(3,infinity)
Next, wisely selects values of x in each of these
intervals, so as to build the sign table
Interval sample text value x f(x)
---------------------------------------------------------
(-infinity,-2) -5 (-5)(-5+2)(-5-3)=
(-5)(-3)(-8) =
-120
(-2,0) -1 (-1)(-1+2)(-1-3)=
(-1)(1)(-4) =4
(0,3) 1 (1)(1+2)(1-3)=
1*3*-2 = -6
(3,infinity) 4 4(4+2)(4-3)=
4*6*1 = 24
So for any x less than -2, the function is negative and the long term
behavior is negative infinity as x grows indefinitely negative.
It is BELOW the x-axis until it hits zero at x=-2.
then it is positive (above the axis), turns around and comes back
down to zero and hits (0,0)
It then is negative , below the x-axis again, turns around and
comes back up to hit (3,0)
finally it is positive forever more for any x>3
you can graph functions at Desmos.
the url is www dot desmos dot com.