8. Aplicando as propriedades das potências, resolva: a) (-7)^1cdot (-7)^2=underline ( ) b) (+3)^5:(+3)^3=underline ( ) c) [(-1)^2]^5=underline ( ) d) (+9)^6cdot (+9)^4=underline ( ) e) (-3)^5cdot (-3)^7:(-3)^8=underline ( ) f) (-21)^3cdot (-21)^8:(-21)^8=underline ( ) g) ([(-17)^1]^1)^2)^2=underline ( ) h) 0^2cdot 9^0=underline ( )

a) $$(-7)^{1}\cdot (-7)^{2} = (-7)^{1+2} = (-7)^{3} = -343$$
b) $$(+3)^{5}:(+3)^{3} = (+3)^{5-3} = (+3)^{2} = 9$$
c) $$[(-1)^{2}]^{5} = [1]^{5} = 1$$
d) $$(+9)^{6}\cdot (+9)^{4} = (+9)^{6+4} = (+9)^{10} = 3486784401$$
e) $$(-3)^{5}\cdot (-3)^{7}:(-3)^{8} = (-3)^{5+7-8} = (-3)^{4} = 81$$
f) $$(-21)^{3}\cdot (-21)^{8}:(-21)^{8} = (-21)^{3+8-8} = (-21)^{3} = -9261$$
g) $$([(-17)^{1}]^{1})^{2})^{2} = [(-17)]^{1\cdot1\cdot2\cdot2} = (-17)^{4} = 83521$$
h) $$0^{2}\cdot 9^{0} = 0^{2}\cdot 1 = 0$$