From the given equation, we have x4+a1x3+a2x2+a3x+a4=(x+1)4+b1(x+1)3+b2(x+1)2+b3(x+1)+b4.
Substitute a1=2, a2=0, a3=1, and a4=6 into the equation, we get x4+2x3+x+6=(x+1)4+b1(x+1)3+b2(x+1)2+b3(x+1)+b4.
Now, let's find the value of f(2,0,1,6), which is b1−b2+b3−b4. To do this, we need to find the values of b1, b2, b3, and b4.
Let's take x=−2 in the equation x4+2x3+x+6=(x+1)4+b1(x+1)3+b2(x+1)2+b3(x+1)+b4. This simplifies to b1−b2+b3−b4=−3.
Therefore, the value of f(2,0,1,6) is −3.