(-2x^4y^5)^3 (-3x^3y^2)^2/(-12x^10y^10)
=-8x^12y^15*9x^6y^4/(-12x^10y^10)
=-72x^18y^19/(-12x^10y^10)
=6x^8y^9
a^3*a^3+(-2a^3)^+(-a^)^3
=a^6+4a^6-a^6
=4a^6
5^k-3=1
log5^k-3=log1
(k-3)log5=0
k-3=0
k=3
5^k-3=1
5^k-3=5^0
k-3=0
k=3