Question

ПОМОГИТЕЕЕЕ Математика ​

Answer 1

$C_n^k=\frac{n!}{k!(n-k)!}\\\\ C_7^4=\frac{7!}{4!(7-4)!}=\frac{5*6*7}{6}=35\\------------\\z_1=-3+5i ; z_2=4-8i\\\\z_1+z_2=-3+4+5i-8i=1-3i\\z_1-z_2=-3+5i-(4-8i)=-3-4+5i+8i=-7+13i\\z_1*z_2=(-3+5i)(4-8i)=-12+24i+20i-40i^2=28+44i$