Объяснение:

z1+z2=(3–4·i)+(2+5·i)= (3+2)+(–4+5)·i=5+i

z1–z2=(3–4·i)–(2+5·i)= (3–2)+(–4–5)·i=1–9·i

z1·z2=(3–4·i)·(2+5·i)=3·2–4·i·2+3·5·i–4·i·5·i=6–8·i+15·i–20·i2=

(так як i2=–1)=6–8·i+15·i+20=26+7·i

z1/z2=(3–4·i)/(2+5·i)= (2–5·i)=(( 3–4·i)(2–5·i))/((2+5·i)(2–5·i))=(3·2–4·i·2–3·5·i+4·i·5·i)/(22–(5·i)2)=(3·2–4·i·2–3·5·i–20)/(22–(5·i)2)=(–14–23·i)/(4+25)=–(14/29)–(23/29)·i