a)

$\frac{-x^2+3}{\left(2-x\right)\left(2+x\right)}$  

dla x = -1 dostajemy 

$\frac{-{\left(-1\right)}^2+3}{\left(2-\left(-1\right)\right)\left(2-1\right)}=\frac{-1+3}{\left(2+1\right)\cdot 1}=\frac{2}{3}$  

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b)

$\frac{x^2-5x+6}{x^8+4x^2+7}$  

dla x = 3 dostajemy

$\frac{3^2-5\cdot 3+6}{3^8+4\cdot 3^2+7}=\frac{9-15+6}{3^8+4\cdot 9+7}=0$    

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c)

$\frac{2x^2+1}{x^3-1}$  

dla x = 2 dostajemy 

$\frac{2\cdot 2^2+1}{2^3-1}=\frac{2\cdot 4+1}{8-1}=\frac{9}{7}$  

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d)

$\frac{32-x^2}{2x^3+8x^2+5x+20}$  

dla x = -3 otrzymujemy 

$\frac{32-{\left(-3\right)}^2}{2\cdot {\left(-3\right)}^3+8\cdot {\left(-3\right)}^2+5\cdot \left(-3\right)+20}=\frac{32-9}{2\cdot \left(-27\right)+8\cdot 9-15+20}=$  

$=\frac{23}{-54+72+5}=\frac{23}{23}=1$