Răspuns:
Ex. 7)
[tex]|a| = \sqrt{3^2+2^2} <=>\sqrt{9+4} =\sqrt{13} \\|a|=\sqrt{5^2+3^2} <=>\sqrt{25+9} =\sqrt{25+9}=\sqrt{34}\\3a+2b = 3(2i+j)+2(0i+3j) = 6i+3j+6j = 6i+9j =>\\=>|3a+2b|=\sqrt{6^2+9^2}=\sqrt{36+81}= \sqrt{117} =3\sqrt{13}[/tex]
Ex. 8)
[tex]a=3i-2j\\b=2i+3j\\=> a+b=(3i-2j)+(2i+3j)=5i+j[/tex]
