You could also consider using std::valarray since it allows exactly the things that you seem to want.
#include
int main()
{
std::valarray a{ 1, 2 }, b{ 2, 4 }, c;
c = a - b; // c is {-1,-2}
a += b; // a is {3,6}
a -= b; // a is {1,2} again
a += {2, 4}; // a is {3,6} again
return 0;
}