Let f(x, y) = x²yi + + (x² + 4y² + 4x)j -Derivative at x, derivative at y -What values must x have so that the derivative at i is 0, does the value of y matter? -What values must y have for the derivative at i to be 0, does the value of x matter? -What values must x have so that the derivative in j is 0, does the value of y matter? -What values must y have for the derivative in j to be 0, does the value of x matter? -Is there a way to find the value of x and y that makes the derivatives at i and j equal to 0?