Question

calcule : 0,85=[1-(1-r)^2]^2

Answer 1

$0,85=[1-(1-r)^{2}]^{2}$
$0,85=[1-(1-r)(1-r)}]^{2}$
$0,85=[1-(1^{2}-r-r+ r^{2}) }]^{2}$
$0,85=[1-(1-2r-r^2)}]^{2}$
$0,85=[2r+r^2)}]^{2}$
$0,85=(2r+r^2)(2r+r^2)$
$0,85=4r^2+2r^3+2r^3+r^4$
$4r^2+2r^3+2r^3+r^4-0,85=0$
$4r^2+4r^3+r^4-0,85=0$
$r^4+4r^3+4r^2-0,85=0$