The slope of the tangent to a curve at any point (x, y) on the curve is -x/y. find the equation of the curve if the point (3, −4) is on the curve.

The differential equation
  dy/dx = -x/y
is a separable differential equation that has the solution
  x^2 + y^2 = c

Substituting the given values for x and y, we find c=25.

The desired equation is
  x^2 + y^2 = 25

The answer would be b ! explanation: the formula for sa *surface area * is 2×l×w+2×l×h+2×w×h so in this case l=4w=12h=8so you use the formula to solve it and it give you the answer of 352^cm^2