a, ( $5^{7}$ + $5^{9}$ ) . ($6^{8}$ + $6^{10}$ ) . ( $2^{4}$ - 4² )
= ( $5^{7}$ + $5^{9}$ ) . ($6^{8}$ + $6^{10}$ ) . ( 4² - 4² )
= ( $5^{7}$ + $5^{9}$ ) . ($6^{8}$ + $6^{10}$ ) .0
= 0
b,(-4)³ . (-4)² - 2³
= $(-4)^{3+2}$ -2³
= $(-4)^{5}$ -2³
= $[(-2).(-2)]^{5}$ -2³
= $(-2)^{5}$. $(-2)^{5}$ -2³
= $(-2)^{10}$ -2³
c, 5.2².2³ -4.( $5^{8}$ : $5^{6}$)
= 5.$2^{5}$ -4.$5^{2}$
= 5.$2^{5}$ -2².$5^{2}$
= 5.2².(2³ -5)