Question

(1,4c-0,7a³)(1,4c+0,7a³)

Answer 1

$\displaystyle\bf\\\Big(1,4c-0,7a^{3} \Big)\Big(1,4c+0,7a^{3} \Big)=\Big(1,4c\Big)^{2} -\Big(0,7a^{3} \Big)^{2}=1,96c^{2} -0,49a^{6}$