if a, b, c are in G.P., then prove that 1/a^2-b^2=1/b^2-c^2-1/b^2
a=A
b=A r
c=A r^2
lhs
1 = 1
A^2+A^2 r^2 A^2(1-r ^2)
rhs
1 - 1
A^2 r^2-A^2 r^4 A^2 r^2
=A^2 r^2-A^2 r^2+A^2 r^4
A^2 r^2(A^2 r^2-A^2 r^4)
= A^2 r^4
A^2 r^2(A^2 r^2-A^2 r^4)
= r^2
A^2 r^2-A^2 r^4
= r^2
A^2 r^2(1-r^2)
= 1
A^2(1-r ^2)
lhs=rhs
hp
b=A r
c=A r^2
lhs
1 = 1
A^2+A^2 r^2 A^2(1-r ^2)
rhs
1 - 1
A^2 r^2-A^2 r^4 A^2 r^2
=A^2 r^2-A^2 r^2+A^2 r^4
A^2 r^2(A^2 r^2-A^2 r^4)
= A^2 r^4
A^2 r^2(A^2 r^2-A^2 r^4)
= r^2
A^2 r^2-A^2 r^4
= r^2
A^2 r^2(1-r^2)
= 1
A^2(1-r ^2)
lhs=rhs
hp