Does anyone know how to do this trig question ?

Find the gradient of f(x,y,z)equals=left parenthesis x squared plus y squared plus z squared right parenthesis superscript negative 1 divided by 2 baseline plus ln left parenthesis x right parenthesis x2+y2+z2−1/2+ln(xyz) at the point left parenthesis negative 2 comma 1 comma negative 2 right parenthesis(−2,1,−2).

What is the length of the missing leg in this right triangle? 18 mm 24 mm 26 mm 32 mm

Given the equation f(x)=a(b)x where the initial value is 40 and the growth rate is 20% what is f(4)