Which selection best completes the blank lines in the proof for line 5 and 6.

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).

Ineed with question three. i don't understand how i'm supposed to achieve 3 marks.

The product of (7x-2) and (20-3x)/4. when x=4