What is the absolute value of square root of -15

Bring the fraction a/a-4 to a denominator of 16-a^2

Find the maximum value of p= 4x + 5y subject to the following constraints :

Sketch the vector field vector f( vector r ) = 8vector r in the xy-plane. select all that apply. the length of each vector is 8. the lengths of the vectors decrease as you move away from the origin. all the vectors point away from the origin. all the vectors point in the same direction. all the vectors point towards the origin. the lengths of the vectors increase as you move away from the origin.