Find the second partial derivatives of the following functions a) z = 3x^2 − 4xy + 15y^2
b) z = 4xe^y
c) z = 6xln(y)

(a) z = 3x ² - 4xy + 15y ²

has first-order partial derivatives

∂z/∂x = 6x - 4y

∂z/∂y = -4x + 30y

and thus second-order partial derivatives

∂²z/∂x ² = 6

∂²z/∂x∂y = -4

∂²z/∂y∂x = -4

∂²z/∂y ² = 30

where ∂²z/∂x∂y = ∂/∂x [∂z/∂y] and ∂²z/∂y∂x = ∂/∂y [∂z/∂x].

(b) z = 4x eʸ

∂z/∂x = 4eʸ

∂z/∂y = 4x eʸ

∂²z/∂x ² = 0

∂²z/∂x∂y = 4eʸ

∂²z/∂y∂x = 4eʸ

∂²z/∂y ² = 4x eʸ

(c) z = 6x ln(y)

∂z/∂x = 6 ln(y)

∂z/∂y = 6x/y

∂²z/∂x ² = 0

∂²z/∂x∂y = 6/y

∂²z/∂y∂x = 6/y

∂²z/∂y ² = -6x/y ²

is means division by fractions

step-by-step explanation:

x= -3 and

step-by-step explanation:

to find the roots of a cubic, use division or factoring to find the factors then set equal to 0. as this is a difference of cubes, it factors into

where a is the cube root of .

here   this is 27 and the cube root of 27 is 3. so we write using the form:

.

set each factor to 0 and solve for x.

x-3=0

x=3

the quadratic expression does not factor and must be solved using the quadratic formula.

where a = 1, b=3, and c=9

this cubic has two complex roots.