Line 1: x² + 3x + 2,  (x + 1)(x + 2),  (x + 1.5)² − 0.25
Line 2: x² + 5x + 6,  (x + 2)(x + 3),  (x + 2.5)² + 6.25

If two expressions are equivalent, then no matter what number
we substitute into them, they will always simplify to the
same numbers.

So let's check by substituting a value, say, x=0 in each:

Line 1: 0² + 3(0) + 2,  (0 + 1)(0 + 2),  (0 + 1.5)² − 0.25
Line 1:             2,               2,        2.25 − 0.25
Line 1:             2,               2,                  2 


Line 2: 0² + 5(0) + 6,  (0 + 2)(0 + 3),  (0 + 2.5)² + 6.25
Line 2:             6,               6,        6.25 + 6.25
Line 2:             6,               6,              12.50

Looks like the answer is Line 1 only.  We have eliminated Line 2.

But we can't be sure about Line 1.  That's because it might 
have just been an accident that we got the same.  So let's 
substitute x=1 in each:

Line 1: 1² + 3(1) + 2,  (1 + 1)(1 + 2),  (1 + 1.5)² − 0.25
Line 1:         1+3+2,             2·3,      (2.5)² − 0.25
Line 1:             6,               6,        6.25 - 0.25 
Line 1:             6,               6,                  6

Yes it's probably Line 1 only. For it's not 
likely that we'd have run into two 
accidents.

Try x = 2

Line 1: 2² + 3(2) + 2,  (2 + 1)(2 + 2),  (2 + 1.5)² − 0.25
Line 1:         4+6+2,             3·4,      (3.5)² − 0.25
Line 1:            12,              12,       12,25 - 0.25 
Line 1:            12,              12,                 12

No doubt about it.  It's Line 1 only.

Edwin