Răspuns:
[tex](5+\dfrac{1}{2}) (5-\dfrac{1}{2})=5\dfrac{1}{2}*4\dfrac{1}{2}=\frac{5*2+1}{2}* \frac{4*2+1}{2} =\dfrac{11}{2} *\dfrac{9}{2}=\dfrac{11*9}{2*2}=\\=\dfrac{99}{4}[/tex]
Explicație pas cu pas: