Solve for x: x/25 > 5

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).

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

Plz hurry evaluate the expression a+b where a=8 and b=19