What is 1 3 of a full rotation

Plz answer asap plz which is a solution to the equation 4b2 − 11b = 28 + 5b2? a) −5 b) −4 c) −3 d) 4

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).

Anyone know? will mark brainliest if you're correct!