Odpowiedź:
[tex]a)\ \ 2x+7,5y-2\ \ \ \ dla\ \ x=3\ \ i\ \ y=4\\\\2x+7,5y-2=2\cdot3+7,5\cdot4-2=6+30-2=36-2=34\\\\\\b)\ \ \frac{x+y}{2}\ \ \ \ dla\ \ x=-7\ \ i\ \ y=11\\\\\frac{x+y}{2}=\frac{-7+11}{2}=\frac{4}{2}=2\\\\\\c)\ \ 4(x-2y)\ \ \ \ dla\ \ x=1,5\ \ i\ \ y=1\\\\4(x-2y)=4(1,5-2\cdot1)=4\cdot(1,5-2)=4\cdot(-0,5)=-2\\\\\\d)\ \ \frac{x}{2}+\frac{3}{y}\ \ \ \ dla\ \ x=2\frac{4}{5}\ \ \ \ i\ \ y=\frac{2}{5} [/tex]
[tex]\dfrac{x}{2}+\dfrac{3}{y}=\dfrac{2\frac{4}{5}}{2}+\dfrac{3}{\frac{2}{5}}=2\dfrac{4}{5}:2+3:\dfrac{2}{5}=\dfrac{\not14^7}{5}\cdot\dfrac{1}{\not2_{1}}+3\cdot\dfrac{5}{2}=\dfrac{7}{5}+\dfrac{15}{2}=1\dfrac{2}{5}+7\dfrac{1}{2}=\\\\\\=1\dfrac{4}{10}+7\dfrac{5}{10}=8\dfrac{9}{10} [/tex]
