Question 972484
Find the vertices and foci of the hyperbola. Draw the graph. 
y^2/25 - x^2/21=1
center: (0,0)
a^2=25
a=5
vertices: (0, 0±a)= (0, 0±5)=(0,-5) and (0,5)
b^2=21
c^2=a^2+b^2=25+21=46
c=√46≈6.8
foci: (0, 0±c)= (0, 0±6.8)=(0,-6.8) and (0,6.8)
see graph below:
y=(25x^2/21+25)^.5
{{{ graph( 300, 300, -10, 10, -10, 10,(25x^2/21+25)^.5,-(25x^2/21+25)^.5) }}}
..
x^2/9 - y^2/16=1
center: (0,0)
a^2=9
a=3
vertices: (0±a, 0)= (0±3, 0)=(-3, 0) and (4, 0)
b^2=16
c^2=a^2+b^2=9+16=25
c=5
foci:(0±c, 0)= (0±5, 0)=(-5, 0) and (5, 0)
see graph below:
y=(16x^2/9-16)^.5
{{{ graph( 300, 300, -10, 10, -10, 10,(16x^2/9-16)^.5,-(16x^2/9-16)^.5) }}}
..