1.5 Lösning 9

\( \, (P + Q) \, = \, 2\,^x \, + \, 2\,^{-x} \; + \; 2\,^x \, - \, 2\,^{-x} \, = \, 2\,^x \, + \, 2\,^x \; + \; 2\,^{-x} \, - \, 2\,^{-x} \, = \, 2 \cdot 2\,^x \)

\( \, (P - Q) \, = \, 2\,^x \, + \, 2\,^{-x} \; - \; (2\,^x \, - \, 2\,^{-x}) \, = \, 2\,^x \, + \, 2\,^{-x} \; - \; 2\,^x \, + \, 2\,^{-x} \, = \, \)

\( \qquad\qquad\; = \, 2\,^x \, - \, 2\,^x \; + \; 2\,^{-x} \, + \, 2\,^{-x} \, = \, 2 \cdot 2\,^{-x} \)

\( \, (P + Q) \cdot (P - Q) \, = \, 2 \cdot 2\,^x \, \cdot \, 2 \cdot 2\,^{-x} \, = \, 2 \cdot 2 \, \cdot \, 2\,^x \cdot 2\,^{-x} \, = \, 4 \, \cdot \, 2\,^{x\,-\,x} \, = \, \)

\( \qquad\qquad\qquad\qquad\;\; = \, 4 \, \cdot \, 2\,^0 \, = \, 4 \)