Hallo ,
Aufgabe 7:
(x-2m)2 =2(x2 -4mn)-(x-2n)2
x2 -4xm +4 m2 = 2 x2 -8mn -( x2 -4xn+4 n2)
x2 -4xm +4 m2 = 2 x2 -8mn - x2 +4xn-4 n2 | -x2
-4xm +4 m2 = -8mn +4xn-4 n2 | -4xn
-4xm -4 xn +4 m2 = -8mn -4 n2 |-4 m2
-4xm -4 xn = -8mn -4 n2 -4 m2 |:4
-xm - xn = -2mn - n2 - m2 |*(-1)
xm + xn = 2mn + n2 + m2
x(m + n) = 2mn + n2 + m2
x(m + n) = (m+n)2 |:(m+n)
x= m+n (m und n≠ 0)