Question

Let f : $\R^3 → \R$ be defined as f(x, y, z) = x3 + y3 + z3 , and let L : $\R^3 → \R$ be the linear map satisfying
$\lim\limits_{(x,y,z)\rightarrow(0,0,0)}\frac{f(1+x,1+y,1+z)-f(1,1,1)-L(x,y,z)}{\sqrt{x^2+y^2+z^2}}=0.$
Then L(1, 2, 4) is equal to ____________. (rounded off to two decimal places)

Answer 1

The correct answer is 20.99 to 21.01.(approx)