Calculus Examples

$lim_{x \to - \infty} \frac{4 x^{3} + 3 x^{2}}{x - 7 x^{2}}$

Step 1

Divide the numerator and denominator by the highest power of $x$ in the denominator, which is $x^{2}$ .

$lim_{x \to - \infty} \frac{\frac{4 x^{3}}{x^{2}} + \frac{3 x^{2}}{x^{2}}}{\frac{x}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2

Simplify terms.

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Step 2.1

Simplify each term.

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Step 2.1.1

Cancel the common factor of $x^{3}$ and $x^{2}$ .

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Step 2.1.1.1

Factor $x^{2}$ out of $4 x^{3}$ .

$lim_{x \to - \infty} \frac{\frac{x^{2} (4 x)}{x^{2}} + \frac{3 x^{2}}{x^{2}}}{\frac{x}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.1.1.2

Cancel the common factors.

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Step 2.1.1.2.1

Multiply by $1$ .

$lim_{x \to - \infty} \frac{\frac{x^{2} (4 x)}{x^{2} \cdot 1} + \frac{3 x^{2}}{x^{2}}}{\frac{x}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.1.1.2.2

Cancel the common factor.

$lim_{x \to - \infty} \frac{\frac{x^{2} (4 x)}{x^{2} \cdot 1} + \frac{3 x^{2}}{x^{2}}}{\frac{x}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.1.1.2.3

Rewrite the expression.

$lim_{x \to - \infty} \frac{\frac{4 x}{1} + \frac{3 x^{2}}{x^{2}}}{\frac{x}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.1.1.2.4

Divide $4 x$ by $1$ .

$lim_{x \to - \infty} \frac{4 x + \frac{3 x^{2}}{x^{2}}}{\frac{x}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.1.2

Cancel the common factor of $x^{2}$ .

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Step 2.1.2.1

Cancel the common factor.

$lim_{x \to - \infty} \frac{4 x + \frac{3 x^{2}}{x^{2}}}{\frac{x}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.1.2.2

Divide $3$ by $1$ .

$lim_{x \to - \infty} \frac{4 x + 3}{\frac{x}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.2

Simplify each term.

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Step 2.2.1

Cancel the common factor of $x$ and $x^{2}$ .

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Step 2.2.1.1

Raise $x$ to the power of $1$ .

$lim_{x \to - \infty} \frac{4 x + 3}{\frac{x^{1}}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.2.1.2

Factor $x$ out of $x^{1}$ .

$lim_{x \to - \infty} \frac{4 x + 3}{\frac{x \cdot 1}{x^{2}} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.2.1.3

Cancel the common factors.

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Step 2.2.1.3.1

Factor $x$ out of $x^{2}$ .

$lim_{x \to - \infty} \frac{4 x + 3}{\frac{x \cdot 1}{x \cdot x} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.2.1.3.2

Cancel the common factor.

$lim_{x \to - \infty} \frac{4 x + 3}{\frac{x \cdot 1}{x \cdot x} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.2.1.3.3

Rewrite the expression.

$lim_{x \to - \infty} \frac{4 x + 3}{\frac{1}{x} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.2.2

Cancel the common factor of $x^{2}$ .

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Step 2.2.2.1

Cancel the common factor.

$lim_{x \to - \infty} \frac{4 x + 3}{\frac{1}{x} + \frac{- 7 x^{2}}{x^{2}}}$

Step 2.2.2.2

Divide $- 7$ by $1$ .

$lim_{x \to - \infty} \frac{4 x + 3}{\frac{1}{x} - 7}$

Step 3

As $x$ approaches $- \infty$ , the fraction $\frac{1}{x}$ approaches $0$ .

$lim_{x \to - \infty} \frac{4 x + 3}{0 - 7}$

Step 4

Since its numerator is unbounded while its denominator approaches a constant number, the fraction $\frac{4 x + 3}{0 - 7}$ approaches infinity.

$\infty$