Resposta:

d)

3(x² - y²) - 10(x + y)(x - y)

3.[(-2)² - (-2)²] - 10.[-2 + (-2)].[(-2) - (-2)]

3.[4 - 4] - 10.[-2 -2].[-2 +2]

3.0 - 10.(-4).(0) = 0 + 0 = 0

e)  (a - b)² - c² ; a =2/3 ; b = 1; c = -1

[tex](\frac{2}{3} -1) - (-1)^{2} =-\frac{1}{3} - 1 = -\frac{4}{3}[/tex]

f) [tex]\frac{1-x^2}{xy+1} = \frac{1-(\frac{1}{2})^2}{(\frac{1}{2}).(-8)+1} =\frac{1-\frac{1}{4}}{-4+1}=\frac{\frac{3}{4}}{-3}=-\frac{1}{4}[/tex]

g) [tex]\frac{x^{2} -y^{2}}{x^{2} +y^{2}} = \frac{(\frac{1}{2} )^{2} -(-2)^{2}}{(\frac{1}{2} )^{2} +(-2)^{2}} = \frac{\frac{1}{4}-4}{\frac{1}{4}+4}= \frac{-\frac{15}{4}}{\frac{17}{4}}=-\frac{15}{17}[/tex]

h) [tex]\frac{5 +\frac{1}{10}}{10 +\frac{1}{5}} = \frac{\frac{51}{10}}{\frac{51}{5}} =\frac{5}{10} =\frac{1}{2}[/tex]