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Which expression is equivalent to [tex]$x^2 + 2x + 2$[/tex]?

A. [tex]$(x+1-i)(x+1-i)$[/tex]
B. [tex][tex]$(x+2)(x+1)$[/tex][/tex]
C. [tex]$(x+1-i)(x+1+i)$[/tex]
D. [tex]$(x-1+i)(x-1-i)$[/tex]


Sagot :

To determine which of the given expressions is equivalent to [tex]\( x^2 + 2x + 2 \)[/tex], we will expand and simplify each expression step by step and compare it to [tex]\( x^2 + 2x + 2 \)[/tex].

### Expression 1: [tex]\((x + 1 - i)(x + 1 - i)\)[/tex]
Expand this expression:
[tex]\[ (x + 1 - i)(x + 1 - i) = (x + 1 - i)^2 \][/tex]
Using the binomial expansion:
[tex]\[ = (x + 1)^2 - 2i(x + 1) + i^2 \][/tex]
[tex]\[ = x^2 + 2x + 1 - 2ix - 2i - 1 \][/tex]
[tex]\[ = x^2 + 2x - 2ix - 2i + i^2 \][/tex]
Since [tex]\( i^2 = -1 \)[/tex]:
[tex]\[ = x^2 + 2x - 2ix - 2i - 1 \][/tex]
[tex]\[ = x^2 + 2x - 2ix - 2i - 1 \][/tex]
This expression simplifies to:
[tex]\[ x^2 + 2x - 2ix - 2i - 1 \neq x^2 + 2x + 2 \][/tex]

### Expression 2: [tex]\((x + 2)(x + 1)\)[/tex]
Expand this expression:
[tex]\[ (x + 2)(x + 1) = x(x + 1) + 2(x + 1) \][/tex]
[tex]\[ = x^2 + x + 2x + 2 \][/tex]
[tex]\[ = x^2 + 3x + 2 \][/tex]
This is not equal to [tex]\( x^2 + 2x + 2 \)[/tex].

### Expression 3: [tex]\((x + 1 - i)(x + 1 + i)\)[/tex]
This expression is a difference of squares:
[tex]\[ (x + 1 - i)(x + 1 + i) = (x + 1)^2 - i^2 \][/tex]
[tex]\[ = x^2 + 2x + 1 - (-1) \][/tex]
[tex]\[ = x^2 + 2x + 1 + 1 \][/tex]
[tex]\[ = x^2 + 2x + 2 \][/tex]
This is equal to [tex]\( x^2 + 2x + 2 \)[/tex].

### Expression 4: [tex]\((x - 1 + i)(x - 1 - i)\)[/tex]
This expression is also a difference of squares:
[tex]\[ (x - 1 + i)(x - 1 - i) = (x - 1)^2 - i^2 \][/tex]
[tex]\[ = x^2 - 2x + 1 - (-1) \][/tex]
[tex]\[ = x^2 - 2x + 1 + 1 \][/tex]
[tex]\[ = x^2 - 2x + 2 \][/tex]
This is not equal to [tex]\( x^2 + 2x + 2 \)[/tex].

From the expanded forms, we can see that the expression equivalent to [tex]\( x^2 + 2x + 2 \)[/tex] is:
[tex]\[ (x + 1 - i)(x + 1 + i) \][/tex]