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Question Number 174672 by Best1 last updated on 08/Aug/22
for what values a and b is the   function differentiable at x=2?  4x−2x^(2 ) x≤2  ax^(3 ) +bx,x>2
$${for}\:{what}\:{values}\:{a}\:{and}\:{b}\:{is}\:{the}\: \\ $$$${function}\:{differentiable}\:{at}\:{x}=\mathrm{2}? \\ $$$$\mathrm{4}{x}−\mathrm{2}{x}^{\mathrm{2}\:} {x}\leqslant\mathrm{2} \\ $$$${ax}^{\mathrm{3}\:} +{bx},{x}>\mathrm{2} \\ $$
Answered by MJS_new last updated on 08/Aug/22
ax^3 +bx=4x−2x^2  with x=2  3ax^2 +b=4−4x with x=2  ⇒ a=−(1/2)∧b=2
$${ax}^{\mathrm{3}} +{bx}=\mathrm{4}{x}−\mathrm{2}{x}^{\mathrm{2}} \:\mathrm{with}\:{x}=\mathrm{2} \\ $$$$\mathrm{3}{ax}^{\mathrm{2}} +{b}=\mathrm{4}−\mathrm{4}{x}\:\mathrm{with}\:{x}=\mathrm{2} \\ $$$$\Rightarrow\:{a}=−\frac{\mathrm{1}}{\mathrm{2}}\wedge{b}=\mathrm{2} \\ $$

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