How do you graph the parabola #Y=1/4x^2# using vertex, intercepts and additional points?

1 Answer
Jul 8, 2016

Full details given on how to interpret a quadratic equation in #x#

Explanation:

Consider the standard form of:#" "y=ax^2+bx+c#

Write this as:#" "y=a(x^2+b/ax)+c#

Note that #c# is the y-intercept
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#color(blue)("Considering the parts of the general equation")#
#color(blue)("in relation to "y=1/4x^2)#

#color(brown)("The shape of the graph")#

If #a>=0 # then the graph is of general shape #uu#

if #a<0# then the graph is of general shape #nn#

#color(brown)(a=1/4 >0 " so the graph is of shape "uu)#
'....................................................................................

#color(brown)("Determine " x_("vertex"))#

#x_("vertex") = (-1/2)xxb/a#

Your equation is #y=1/4x^2+0x+0->y=1/4[x^2+(4xx0)x]+0#

So #b/a=0#

#color(brown)(=> x_("vertex")=(-1/2)xx0=0)#
So the graph is symmetrical about the y-axis
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#color(brown)("Determine " y_("vertex"))#

Substitute #x=0# giving

#color(blue)(y=1/4x^2+0x+0)color(brown)(" "->" "y_("vertex")=1/4xx0^2 = 0)#
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#color(brown)(" Vertex "->(x,y)=(0,0))#

#color(green)(=>y_("intercept")=0)#

#color(green)(=>x_("intercept") = 0" the x-axis is a tangent to the")# #color(green)("curve at the vertex")#
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#color(brown)(" Determine any other points")#

Substitute values for #x# into the equation and determine the corresponding value of #y#

Suppose #x=2# then #y=1/4(2)^2 = 4/4=1#

This is also true for #x=-2#

So at #y=1" ; " x= +-2" as it is symmetrical about the y-axis"#