MHB Derivative: Simplifying an Equation

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The discussion focuses on simplifying a complex equation involving derivatives. The transformation from the original equation to the simplified form is achieved through algebraic manipulation, including cancellation and the FOIL method. Participants clarify the steps involved, emphasizing the importance of correctly applying these techniques to reach the final result. The simplification ultimately leads to a clearer expression of the equation. Understanding these steps is crucial for mastering derivative simplification.
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How does this equation:

$$\dfrac{12x\sqrt{2x^3+3x+2}-\frac{\left(6x^2+3\right)^2}{2\sqrt{2x^3+3x+2}}}{2\left(2x^3+3x+2\right)}$$

becomes this equation

$${12x^4+36x^2+48x-9}frac{4\left(2x^3+3x+2\right)^\frac{3}{2}}$$
 
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$$\frac{12x\sqrt{2x^3+3x+2}-\dfrac{\left(6x^2+3\right)^2}{2\sqrt{2x^3+3x+2}}}{2\left(2x^3+3x+2\right)}\cdot\frac{2\sqrt{2x^3+3x+2}}{2\sqrt{2x^3+3x+2}}=\frac{24x(2x^3+3x+2)-(6x^2+3)^2}{4\left(2x^3+3x+2\right)^{\frac{3}{2}}}=\frac{48x^4+72x^2+48x-36x^4-36x^2-9}{4\left(2x^3+3x+2\right)^{\frac{3}{2}}}=\frac{12x^4+36x^2+48x-9}{4\left(2x^3+3x+2\right)^{\frac{3}{2}}}$$
 
MarkFL said:
$$\frac{12x\sqrt{2x^3+3x+2}-\dfrac{\left(6x^2+3\right)^2}{2\sqrt{2x^3+3x+2}}}{2\left(2x^3+3x+2\right)}\cdot\frac{2\sqrt{2x^3+3x+2}}{2\sqrt{2x^3+3x+2}}=\frac{24x(2x^3+3x+2)-(6x^2+3)^2}{4\left(2x^3+3x+2\right)^{\frac{3}{2}}}=\frac{48x^4+72x^2+48x-36x^4-36x^2-9}{4\left(2x^3+3x+2\right)^{\frac{3}{2}}}=\frac{12x^4+36x^2+48x-9}{4\left(2x^3+3x+2\right)^{\frac{3}{2}}}$$

ahh okay i see it now cancels out then foil for the left side then. thank you
 
There are probably loads of proofs of this online, but I do not want to cheat. Here is my attempt: Convexity says that $$f(\lambda a + (1-\lambda)b) \leq \lambda f(a) + (1-\lambda) f(b)$$ $$f(b + \lambda(a-b)) \leq f(b) + \lambda (f(a) - f(b))$$ We know from the intermediate value theorem that there exists a ##c \in (b,a)## such that $$\frac{f(a) - f(b)}{a-b} = f'(c).$$ Hence $$f(b + \lambda(a-b)) \leq f(b) + \lambda (a - b) f'(c))$$ $$\frac{f(b + \lambda(a-b)) - f(b)}{\lambda(a-b)}...

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