Answer: C
Expression= 2 (x^2) + 3 (y^2) - 4x - 12y + 18
For extreme values of expression, d/dx(expression) =0
Differentiating with respect to x,
d/dx(expression) = 4x - 4= 0
Therefore, x= 1
Differentiating with respect to y,
d/dy(expression) = 6y - 12= 0
Therefore, y= 2
Substituting values x=1, y=2 in expression,
we get value = 4
It can be ascertained that this extreme value is minimum as d^2/dx^2(expression) = 4 (positive) and d^2/dy^2(expression) = 6 (positive)
Note: Differentiation is not tested on the GMAT, but following little information helps
1. d/dx(constant) = 0
2. d/dx(x^n) = n * x^(n-1)
3. d/dx(c*x) = c ; where c = constant
4. Expression has extreme values at d/dx(expression)=0
; d2/dx^2(expression) = positive signifies minimum value
; d2/dx^2(expression) = negative signifies maximum value
_________________
__________________________________
Kindly press "+1 Kudos" if the post helped