Question

Me ajudem nessas 2 questões com calculo pfvv

Answer 1

72)

$\dfrac{\frac{(x +y)}{xy} }{\frac{x^{2} -y^{2} }{xy} } = \frac{(x +y) * xy}{(x^{2} -y^{2}) *xy} = \frac{(x +y)}{x^{2} -y^{2} } = \frac{(x+y)}{(x+y)*(x-y)} = \frac{1}{(x-y)}$

x -y = 4

$\frac{1}{4} = 0.25$

$\boxed{\underline{\mathbf{R}\mathsf{esposta\to (a) }}}$

73)

$\boxed{\mathsf{a^{2} -b^{2} = (a-b)*(a+b)}}$

$\frac{x^{4}-1}{(x -1) * (x^{2} +1)} = \frac{(x^{2}+1)*(x^{2}-1)}{(x-1)*(x^{2}+1)} = \frac{(x^{2}-1)}{(x-1)} = \frac{(x+1)(x-1)}{(x-1)}= (x+1)$

x = 1999

1999 + 1 = 2000

$\boxed{\underline{\mathbf{R}\mathsf{esposta\to (a) }}}$