Question 6(ii)
Evaluate:
(58)−7×(85)−4
(58)−7×(85)−4=5−78−7×8−45−4 [∵(ab)m=ambm]=5−7−(−4)×8−4−(−7) [∵am÷an=am−n]=5−7+4×8−4+7=5−3×83=8353 [∵a−m=1am]=512125
Alternative:
(58)−7×(85)−4
= (85)7×(85)−4 [∵a−m=1am]
= (85)7+(−4) [∵am×an=am+n]
= (85)(7−4)
= (85)3
=512125