Question 763198
Graph the ellipse and locate the foci ? 
X^2/64 + y^2/16 = 1
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Given ellipse has a horizontal major axis with center at (0,0)
Its standard form of equation: {{{x^2/a^2+(y-k)^2/b^2}}}, a>b
For given ellipse:
a^2=64
a=8
b^2=16
b=4
c^2=a^2-b^2=64-16=48
c=√48≈6.93
foci:(0±c,0)=(±6.93,0)=(-6.93,0) and (6.93,0)
see graph below:
y=±(16-x^2/4)^.5

{{{ graph( 300, 300, -10,10, -10, 10,(16-x^2/4)^.5,-(16-x^2/4)^.5) }}}