Diagonal multiplication

3a^2=3a^2-2ab-b^2

b^2=-2ab

B is not equal to 0.

b=-2a

replace

{[2(9a^2-4b^2)]/(4a^2-9b^2)}-{[(3a+2b)/(2a+3b)]^2}-

{[(3a-2b)/(2a-3b)]^2}

={[2(9a^2-4*4a^2)]/(4a^2-9*4a^2)}-{[(3a+2*(-2a))/(2a+3*(-2a))]^2}-{[(3a-2(-2a))/(2a-3*(-2a))]^2}

={[- 14a^2]/(-32a^2)}-{[-a)/(-4a)]^2}-{[7a)/(8a)]^2}

=(7/ 16)- 1/ 16-49/64

=-25/64