Get personalized answers to your unique questions on IDNLearn.com. Get prompt and accurate answers to your questions from our community of experts who are always ready to help.

Find the limit:

[tex][tex]$\operatorname{Lim}_{x \rightarrow 1} \frac{x^4+x^3+x^2+x-4}{x-1}$[/tex][/tex]


Sagot :

Certainly! Let’s evaluate the limit:

[tex]\[ \lim_{{x \to 1}} \frac{x^4 + x^3 + x^2 + x - 4}{x - 1} \][/tex]

### Step 1: Recognize Indeterminate Form

First, plug [tex]\( x = 1 \)[/tex] into the expression to see what form we get:
[tex]\[ \frac{1^4 + 1^3 + 1^2 + 1 - 4}{1 - 1} = \frac{1 + 1 + 1 + 1 - 4}{0} = \frac{0}{0} \][/tex]

This is an indeterminate form, so we need to simplify or transform the expression to evaluate the limit.

### Step 2: Factor the Numerator

Since direct substitution gives an indeterminate form, we need to factor the numerator and see if there's a way to cancel out the [tex]\( x - 1 \)[/tex] in the denominator.

Consider the expression [tex]\( x^4 + x^3 + x^2 + x - 4 \)[/tex]. We want to factor it such that we can divide out the [tex]\( x - 1 \)[/tex].

### Step 3: Polynomial Division (optional method)

Alternatively, since this division isn't straightforward to factor by inspection, we use polynomial division or synthetic division to rewrite the numerator as a product involving [tex]\( x - 1 \)[/tex].

But for conciseness, we might skip the long division steps here given that it leads us to the factored form. When [tex]\( x = 1 \)[/tex] is a root, our polynomial [tex]\( x^4 + x^3 + x^2 + x - 4 \)[/tex] can be expressed as:

[tex]\[ (x - 1)Q(x) \][/tex]

where [tex]\( Q(x) \)[/tex] is a polynomial of degree 3.

### Step 4: Direct Simplification and the Limit

Once we factor and cancel the common term [tex]\( x - 1 \)[/tex] in the numerator and denominator, we are left with:
[tex]\[ \lim_{{x \to 1}} Q(x) \][/tex]

If we perform this factorization (which can be checked using division or algebraic manipulation principles), we would find:

[tex]\[ x^4 + x^3 + x^2 + x - 4 = (x - 1)(x^3 + 2x^2 + 3x + 4) \][/tex]

### Step 5: Substitute and Simplify

Thus, our limit becomes:
[tex]\[ \lim_{{x \to 1}} \frac{(x - 1)(x^3 + 2x^2 + 3x + 4)}{x - 1} = \lim_{{x \to 1}} (x^3 + 2x^2 + 3x + 4) \][/tex]

As [tex]\( x \to 1 \)[/tex], substitute [tex]\( x = 1 \)[/tex] into [tex]\( x^3 + 2x^2 + 3x + 4 \)[/tex]:
[tex]\[ 1^3 + 2(1^2) + 3(1) + 4 = 1 + 2 + 3 + 4 = 10 \][/tex]

Thus, the limit is:
[tex]\[ \boxed{10} \][/tex]