Calculus · real student question

Find the derivative of y = (1/10)x^5 + x^4 + 3x - sqrt(3).

Question

Find the derivative of y=110x5+x4+3x3.y=\frac{1}{10}x^{5}+x^{4}+3x-\sqrt3 .

Step-by-step solution

  1. Differentiate the leading term and simplify the coefficient. The power rule gives (110x5)=1105x4=510x4=12x4.\left(\frac{1}{10}x^{5}\right)^{\prime}=\frac{1}{10}\cdot 5x^{4}=\frac{5}{10}x^{4}=\frac12 x^{4}. A frequent error here is to write 2x42x^{4}, which would come from dividing 1010 by 55 instead of multiplying 110\frac1{10} by 55.

  2. Differentiate the quartic term. (x4)=4x3.\left(x^{4}\right)^{\prime}=4x^{3}.

  3. Differentiate the linear term. (3x)=3.\left(3x\right)^{\prime}=3 .

  4. Recognise the irrational constant. 3\sqrt3 is a fixed number, roughly 1.7321.732, not a function of xx, so (3)=0\left(-\sqrt3\right)^{\prime}=0. The presence of a radical does not change this.

  5. Assemble the derivative. y=12x4+4x3+3.y^{\prime}=\frac12 x^{4}+4x^{3}+3 . Note that y>0y^{\prime}>0 whenever x>0x>0, and at x=0x=0 the derivative equals 33, so the curve is rising at the origin.

Answer

y=12x4+4x3+3y^{\prime}=\frac{1}{2}x^{4}+4x^{3}+3

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