Having in view that quadrilatic function has the general form as y=a x2 +b x +c where a , b , c ∈ R and a ≠ 0, I analysed the
followig forms:
A) In the following form of quadrilatic ecuation the midle term (from a x 2+ b x+ c ) is missing (b x term)
y=x 2 +2 y=x 2 +5 y=x 2−12
a=1 ; b=0 ,c =2 a=1 ; b=0 ,c =5 a=1 ; b=0 ,c =−12
1 f ( x )=−x 2 +3 3
f ( x )=x 2− f ( x )=−x 2−
2 a=−1 ; b=0 , c=3 4
−1 −3
a=1 ; b=0 ,c = a=−1 ; b=0 , c=
2 4
Function Direction of opening Vertex Axis of symmetry X-Intercept
2
y=x +2 up ( 2 ; 0) x=0 no points
y=x 2 +5 up (5 ; 0) x=0 no points
y=x 2−12 up (−12 ; 0 ) x=0 two points .....
1 up −1 x=0 two points .....
y=x 2−
2 ( 2
;0)
y−x 2 +3 down (3 ; 0) x=0 two points ....
3 down −3 x=0 no points
y=−x2 −
4 ( 4
;0)
General Conclusion
General form: f ( x )=a x 2 +c
If a> 0 , direction of opening is up
If a< 0 , direction of opening is down
Vertex is ( c ; 0 )
Axis of symmetry x=0
If a> 0 and c >0 , there is no point of intersection of the Graph with Ox axes
If a< 0 and c <0 , there is no point of intersection of the Graph with Ox axes
B) quadrilatic ecuation
2 2 2
y= ( x −2 ) y= ( x −4 ) 1
y= x− ( ) 2
2 2 2
y= ( x +2 ) y= ( x +3 ) 3
( )
y= x +
2
Function Direction of opening Vertex Axis of symmetry X-Intercept Y-Intercept
y= ( x −2 ) 2 up ( 2 ; 0) x=2 one point, in ( 2 ; 0 ) (0 ; 4 )
y= ( x −4 )
2 up ( 4 ; 0) x=4 one point in( 4 ; 0 ) ( 0 ; 16 )
2
1
1
( 12 ; 0) ( 12 ; 0) (0 ; 14 )
up
( )
y= x−
2
x=
2
one point in
y= ( x +2 )
2 up (−2 ; 0 ) x=−2 one point in (−2 ; 0 ) (0 ; 4 )
y= ( x +3 )2 up (−3 ; 0 ) x=−3 one point in (−3 ; 0 ) (0 ; 9)
2
2 −2
( −23 ; 0 ) (0 ; 49 )
up −2
( )
y= x +
3 ( 3
;0 ) x=
3
one point in
General Conclusion
2
General form: y= ( x ± c )
direction of opening is always up
Vertex is ( ∓ c ; 0 )
Axis of symmetry x=∓c
X-Intercept only in one point ( ∓ c ; 0 )
Y-Intercept only in one point ( 0 ; c 2 )
C) quadrilatic ecuation
y=x 2 y=3 x 2 y=0.5 x 2
y=−x2 y=−2 x 2 y=
−9 2
x
2
Function Direction of opening Vertex Axis of symmetry X-Intercept Y-Intercept
y=x 2 up ( 0 ; 0) x=0 one point, in ( 0 ; 0 ) no points
y=3 x 2 up ( 0 ; 0) x=0 one point, in ( 0 ; 0 ) no points
y=0.5 x 2 up ( 0 ; 0) x=0 one point, in ( 0 ; 0 ) no points
y=−x2 down ( 0 ; 0) x=0 one point, in ( 0 ; 0 ) no points
y=−2 x 2 down ( 0 ; 0) x=0 one point, in ( 0 ; 0 ) no points
−9 2 down ( 0 ; 0) x=0 one point, in ( 0 ; 0 ) no points
y= x
2
General Conclusion
General form: y=a x2
If a> 0 , direction of opening is up
If a< 0 , direction of opening is down
Vertex is always ( 0 ; 0 )
Axis of symmetry x=0
X-Intercept only in one point ( 0 ; 0 )
Y-Intercept no intercept