Question

A cuboid of dimensions 4×2×3 is made of smaller cubes of dimension 1×1×1. If you are the observer how many cubes will not have any face visible to you?
A)9
B)11
C)12
D)14
​

Answer 1

Answer:

12

Step-by-step explanation:

Answer 2

Answer:

12

Step-by-step explanation:

This implies that

x2+2ax=4x−4a−13

or

x2+2ax−4x+4a+13=0

or

x2+(2a−4)x+(4a+13)=0

Since the equation has just one solution instead of the usual two distinct solutions, then the two solutions must be same i.e. discriminant = 0.

Hence we get that

(2a−4)2=4⋅1⋅(4a+13)

or

4a2−16a+16=16a+52

or

4a2−32a−36=0

or

a2−8a−9=0

or

(a−9)(a+1)=0

So the values of a are −1 and 9.