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If 
f(x)=(x^(2)+1)^(3), what is 
lim_(x rarr-1)(f(x)-f(-1))/(x+1)?

If f(x)=(x2+1)3 f(x)=\left(x^{2}+1\right)^{3} , what is limx1f(x)f(1)x+1? \lim _{x \rightarrow-1} \frac{f(x)-f(-1)}{x+1} ?

Full solution

Q. If f(x)=(x2+1)3 f(x)=\left(x^{2}+1\right)^{3} , what is limx1f(x)f(1)x+1? \lim _{x \rightarrow-1} \frac{f(x)-f(-1)}{x+1} ?
  1. Substitute x=1x = -1: First, substitute x=1x = -1 into f(x)f(x) to find f(1)f(-1).\newlinef(1)=((1)2+1)3=(1+1)3=23=8f(-1) = ((-1)^2 + 1)^3 = (1 + 1)^3 = 2^3 = 8.
  2. Simplify expression: Now, simplify the expression (f(x)f(1))/(x+1)(f(x) - f(-1)) / (x + 1).(f(x)f(1))/(x+1)=((x2+1)38)/(x+1)(f(x) - f(-1)) / (x + 1) = ((x^2 + 1)^3 - 8) / (x + 1).
  3. Factorize the numerator: To find the limit as xx approaches 1-1, we need to simplify the numerator. Notice that x2+1=2x^2 + 1 = 2 when x=1x = -1, so we can factorize the numerator using the difference of cubes: (x2+1)38=(2)38=88=0(x^2 + 1)^3 - 8 = (2)^3 - 8 = 8 - 8 = 0. This shows that the numerator is zero at x=1x = -1.
  4. Check denominator: Since the numerator is zero at x=1x = -1, we need to check if the denominator also becomes zero to avoid division by zero.\newlineAt x=1x = -1, the denominator x+1=1+1=0x + 1 = -1 + 1 = 0.
  5. Apply L'Hopital's Rule: Both the numerator and denominator are zero at x=1x = -1, indicating a 0/00/0 form. We apply L'Hopital's Rule:\newlineDifferentiate the numerator and the denominator separately.\newlineNumerator: ddx[(x2+1)3]=3(x2+1)22x=6x(x2+1)2\frac{d}{dx}[(x^2 + 1)^3] = 3(x^2 + 1)^2 \cdot 2x = 6x(x^2 + 1)^2.\newlineDenominator: ddx[x+1]=1\frac{d}{dx}[x + 1] = 1.
  6. Find limit of derivatives: Now, find the limit of the derivatives as xx approaches 1-1: limx1[6x(x2+1)21]=6(1)(1+1)2=6(1)(2)2=24\lim_{x \to -1} \left[\frac{6x(x^2 + 1)^2}{1}\right] = 6(-1)(1 + 1)^2 = 6(-1)(2)^2 = -24.

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