x-2y+4=0 is a common tangent to y2=4x & x24+y2b2=1 Then the value of b and the other common tangent are given by:
x+2y + 4 = 0
x- 2y -4 =0
x-2y+4=0is a tangent to x24+y2b2=1
The other tangent must be reflection of x-2y+4 = 0 in the x-axis since both curves are symmetrical about x-axis.
x+2y+4=0 is the other common tangent.