Giải bài 2 trang 136 – SGK môn Giải tích lớp 12
Tính \(\alpha +\beta ,\,\alpha -\beta\) với:
a) \(\alpha =3,\,\beta =2i \);
b) \(\alpha =1-2i,\,\beta =6i\);
c) \(\alpha =5i,\,\beta =-7i\);
d) \(\alpha =15,\,\beta =4-2i\).
Nhắc lại:
\(z+z'=(a+bi)+(a'+b'i)=(a+a') +(b+b')i\)
a) \(\alpha =3,\,\beta =2i \)
\( \left\{ \begin{aligned} & \alpha +\beta \,=3+2i \\ & \alpha -\beta =3-2i \\ \end{aligned} \right. \)
b) \(\alpha =1-2i,\,\beta =6i\)
\(\left\{ \begin{aligned} & \alpha +\beta =1-2i+6i=1+4i\, \\ & \alpha -\beta =1-2i-6i=1-8i \\ \end{aligned} \right. \)
c) \(\alpha =5i,\,\beta =-7i\)
\(\left\{ \begin{aligned} & \alpha +\beta \,=5i-7i=-2i \\ & \alpha -\beta =5i+7i=12i \\ \end{aligned} \right. \)
d) \(\alpha =15,\,\beta =4-2i\)
\(\left\{ \begin{aligned} & \alpha +\beta =15+4-2i=19-2i\, \\ & \alpha -\beta =15-4+2i=11+2i \\ \end{aligned} \right. \)