Calculus Examples

$lim_{x \to 0} \frac{\frac{{(x + h)}^{2} - 6}{3 {(x + h)}^{2}} - \frac{x^{2} - 6}{3 x^{3}}}{h}$

Step 1

Combine terms.

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Step 1.1

To write $\frac{{(x + h)}^{2} - 6}{3 {(x + h)}^{2}}$ as a fraction with a common denominator, multiply by $\frac{x^{3}}{x^{3}}$ .

$lim_{x \to 0} \frac{\frac{{(x + h)}^{2} - 6}{3 {(x + h)}^{2}} \cdot \frac{x^{3}}{x^{3}} - \frac{x^{2} - 6}{3 x^{3}}}{h}$

Step 1.2

To write $- \frac{x^{2} - 6}{3 x^{3}}$ as a fraction with a common denominator, multiply by $\frac{{(x + h)}^{2}}{{(x + h)}^{2}}$ .

$lim_{x \to 0} \frac{\frac{{(x + h)}^{2} - 6}{3 {(x + h)}^{2}} \cdot \frac{x^{3}}{x^{3}} - \frac{x^{2} - 6}{3 x^{3}} \cdot \frac{{(x + h)}^{2}}{{(x + h)}^{2}}}{h}$

Step 1.3

Write each expression with a common denominator of $3 {(x + h)}^{2} x^{3}$ , by multiplying each by an appropriate factor of $1$ .

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Step 1.3.1

Multiply $\frac{{(x + h)}^{2} - 6}{3 {(x + h)}^{2}}$ by $\frac{x^{3}}{x^{3}}$ .

$lim_{x \to 0} \frac{\frac{({(x + h)}^{2} - 6) x^{3}}{3 {(x + h)}^{2} x^{3}} - \frac{x^{2} - 6}{3 x^{3}} \cdot \frac{{(x + h)}^{2}}{{(x + h)}^{2}}}{h}$

Step 1.3.2

Multiply $\frac{x^{2} - 6}{3 x^{3}}$ by $\frac{{(x + h)}^{2}}{{(x + h)}^{2}}$ .

$lim_{x \to 0} \frac{\frac{({(x + h)}^{2} - 6) x^{3}}{3 {(x + h)}^{2} x^{3}} - \frac{(x^{2} - 6) {(x + h)}^{2}}{3 x^{3} {(x + h)}^{2}}}{h}$

Step 1.3.3

Reorder the factors of $3 {(x + h)}^{2} x^{3}$ .

$lim_{x \to 0} \frac{\frac{({(x + h)}^{2} - 6) x^{3}}{3 x^{3} {(x + h)}^{2}} - \frac{(x^{2} - 6) {(x + h)}^{2}}{3 x^{3} {(x + h)}^{2}}}{h}$

Step 1.4

Combine the numerators over the common denominator.

$lim_{x \to 0} \frac{\frac{({(x + h)}^{2} - 6) x^{3} - (x^{2} - 6) {(x + h)}^{2}}{3 x^{3} {(x + h)}^{2}}}{h}$

Step 2

Simplify the limit argument.

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Step 2.1

Multiply the numerator by the reciprocal of the denominator.

$lim_{x \to 0} \frac{({(x + h)}^{2} - 6) x^{3} - (x^{2} - 6) {(x + h)}^{2}}{3 x^{3} {(x + h)}^{2}} \cdot \frac{1}{h}$

Step 2.2

Multiply $\frac{({(x + h)}^{2} - 6) x^{3} - (x^{2} - 6) {(x + h)}^{2}}{3 x^{3} {(x + h)}^{2}}$ by $\frac{1}{h}$ .

$lim_{x \to 0} \frac{({(x + h)}^{2} - 6) x^{3} - (x^{2} - 6) {(x + h)}^{2}}{3 x^{3} {(x + h)}^{2} h}$

Step 3

Since the numerator is negative and the denominator $3 x^{3} {(x + h)}^{2} h$ approaches zero and is less than zero for $x$ near $0$ on both sides, the function increases without bound.

$\infty$