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Să se calculeze :

[tex] \int6x {(3 {x}^{2} + 1)}^{7} \: dx , \: x\:\in\:\mathbb{R}[/tex]


Răspuns :

  1. Facem #schimbarea_de_variabila 3x^2+1=t ⇒ 6x dx= dt
  2. Prin urmare integrala va deveni ∫ t⁷ dt = t⁸/8+C , iar inlocuind obtinem
  3. (3x²+1)⁸/8+C
  4. Hope you understood!

fie 3x²+1=u

atunci 6xdx=du

∫6x*(3x²+1)^7dx= ∫(3x²+1)^7*6xdx=∫u^7du=u^/8=(1/8)*(3x²+1)^7 +C

as prima schimbarede variabila as that!