Răspuns :
E(x)=(x-1)²-(x-2)²+(1-x)²-(2-x)²
Observam ca (x-1)²=(1-x)² si (x-2)²=(2-x)².
Deci
E(x)=2(x-1)²-2(x-2)²=2[(x-1)²-(x-2)²]=
2(x-1+x-2)(x-1-x+2)=
2(2x-3)×1=4x-6.
Observa ca am folosit: a²-b²=(a-b)(a+b)
E(x)=(x-1)²-(x-2)²+(1-x)²-(2-x)²
Observam ca (x-1)²=(1-x)² si (x-2)²=(2-x)².
Deci
E(x)=2(x-1)²-2(x-2)²=2[(x-1)²-(x-2)²]=
2(x-1+x-2)(x-1-x+2)=
2(2x-3)×1=4x-6.
Observa ca am folosit: a²-b²=(a-b)(a+b)