How do you graph and label the vertex and axis of symmetry of #y=(x+1)^2+3#?

1 Answer
Jan 24, 2018

See below.

Explanation:

#y=(x+1)^2+3# , is in the form:

#y=a(x-h)^2+k#

Where a is the coefficient of #x^2#, h is the axis of symmetry and k is the maximum/minimum value.

Notice that a #=1# is positive, so the parabola will be of this form: #uuu#. This means it has a minimum value.

The minimum or maximum value always occurs where the #x# coordinate is #h# and the #y# coordinate is #k# i.e.:

#(h,k)#

From our equation this is:

#color(blue)((-1 ,3)#

Notice that #h=-1# and not #1#. This is because we have #(x-h)^2#, so when #h# is negative, #(x-(-1))^2=(x+1)^2#

This coordinate can be used for graphing. Other useful points are:

#y# axis intercept occurs when #x=0#

#y=((0)+1)^2+3=4#

coordinate:

#color(blue)((0,4)#

#x# axis intercepts occur when #y=0#:

#(x+1)^2+3=0#

#(x+1)^2=-3#

#x=-1+sqrt(-3)# ( This is a non real value, so no x axis intercepts ).

Other point for graphing will have to be found by plugging in values for #x# and calculating the corresponding values of #y#.

Values could be:

#x=1->(1+1)^2+3=7->color(blue)((1,7)#

#x=2->(2+1)^2+3=12->color(blue)((2,12)#

#x=-3->(-3+1)^2+3=7->color(blue)((-3,7)#

#x=-4->(-4+1)^2+3=12->color(blue)((-4,12)#

The more points you plot the more accurate the curve will be:

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Join the points and mark the axis of symmetry ( You could use a dashed line for this ). Mark the minimum value ( You can use a dot for this ).

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