Verbal Reasoning - Mental Ability Questions

3  1  7  3  7

3  1  7  3  8

7  1  7  3  9

At these places 1, 7, 3 appeared together

Here the given expression, 

X2 + X2 is an algebraic expression. Here in this expression the terms are like terms. Now to add them, add their coefficients.

Here in the given expression, the like terms are two X2

Hence, adding their coefficients i.e, 1 + 1 = 2

Therefore, 

X2 + X2 = 2X2.

Here given formula is 

a2 + b2 + c2 -ab- bc - ca = 0

and it is possible if and only if a = b = c.

From the trial and error method, 

1) Let a = b = c = 1

Now substitute these values of a, b, c in the above formula.

We get 1 + 1 + 1 - 1 - 1 - 1 = 3 - 3 = 0

2) Now, let a = b = c = 4

Now substitute these values of a, b, c in the above formula.

We get 16 + 16 + 16 - 16 - 16 - 16 = 48 - 48 = 0.

Hence, it is possible that 

a2 + b2 + c2 -ab- bc - ca = 0 iff a = b = c.