Because flutter_math <0.3.0-nullsafety.0 depends on tuple ^1.0.3 which depends on quiver >=0.22.0 <3.0.0, flutter_math <0.3.0-nullsafety.0 requires quiver >=0.22.0 <3.0.0.
(1) So, because google_sign_in_platform_interface >=2.0.0 depends on quiver ^3.0.0, flutter_math <0.3.0-nullsafety.0 is incompatible with google_sign_in_platform_interface >=2.0.0.
Because flutter_math <0.3.0-nullsafety.0 depends on tuple ^1.0.3 which depends on quiver >=0.22.0 <3.0.0, flutter_math <0.3.0-nullsafety.0 requires quiver >=0.22.0 <3.0.0.
(1) So, because google_sign_in_platform_interface >=2.0.0 depends on quiver ^3.0.0, flutter_math <0.3.0-nullsafety.0 is incompatible with google_sign_in_platform_interface >=2.0.0.