c) a^2 +ab/ b -a : a +b/ 2a^2 -2b^2 ;

c) a2+abb−a:a+b2a2−2b2=a(a+b)b−a:a+b2(a+b)(a−b)

=−a(a+b)a−b:12(a−b)=−2a(a+b)(a−b)a−b

= −2a(a + b) = −2a2 – 2b2.