Non mi torna

2·x^2 + (1/3·x - (2/3·x^2 + x - 1/3·x^2) + 1/2·x^2) + 2/3·x - 1/6·x^2=

=2·x^2 + (1/3·x - (x^2/3 + x) + 1/2·x^2) + 2/3·x - 1/6·x^2=

=2·x^2 + (x^2/6 - 2·x/3) + 2/3·x - 1/6·x^2=

=2·x^2

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((- 3·a·b^2)^3 - 15·a^3·b·(- 4/5·b^5) - (4·a)^2·1/6·a·b^4·(- 3·b^2))^2=

=(- 27·a^3·b^6 - (- 12·a^3·b^6) - (- 8·a^3·b^6))^2=

=(- 27·a^3·b^6 + 12·a^3·b^6 + 8·a^3·b^6)^2=

=(- 7·a^3·b^6)^2 = 49·a^6·b^12

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$\small 2x^2+\left[\dfrac{1}{3}x-\left(\dfrac{2}{3}x^2+x-\dfrac{1}{3}x^2\right)+\dfrac{1}{2}x^2\right]+\dfrac{2}{3}x-\dfrac{1}{6}x^2=$

$\small = 2x^2+\left[\dfrac{1}{3}x-\left(\dfrac{1}{3}x^2+x\right)+\dfrac{1}{2}x^2\right]+\dfrac{2}{3}x-\dfrac{1}{6}x^2=$

$\small = 2x^2+\left[\dfrac{1}{3}x-\dfrac{1}{3}x^2-x+\dfrac{1}{2}x^2\right]+\dfrac{2}{3}x-\dfrac{1}{6}x^2=$

$\small = 2x^2+\left[\dfrac{1}{3}x-x-\dfrac{1}{3}x^2+\dfrac{1}{2}x^2\right]+\dfrac{2}{3}x-\dfrac{1}{6}x^2=$

$\small = 2x^2+\left[\dfrac{x-3x}{3}+\dfrac{-2x^2+3x^2}{6}\right]+\dfrac{2}{3}x-\dfrac{1}{6}x^2=$

$\small = 2x^2+\left[-\dfrac{2}{3}x+\dfrac{1}{6}x^2\right]+\dfrac{2}{3}x-\dfrac{1}{6}x^2=$

$\small = 2x^2-\cancel{\dfrac{2}{3}x}+\cancel{\dfrac{1}{6}x^2}+\cancel{\dfrac{2}{3}x}-\cancel{\dfrac{1}{6}x^2}=$

$\small = 2x^2$

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$\small \left[\left(-3ab^2\right)^3-\cancel{15}^3a^3b·\left(-\dfrac{4}{\cancel5_1}b^5\right)-\left(4a\right)^2·\dfrac{1}{6}ab^4·\left(-3b^2\right)\right]^2 =$

$\small = \left[-27a^3b^6-3a^3b·\left(-4b^5\right)-\cancel{16}^8a^2·\dfrac{1}{\cancel6_3}ab^4·\left(-3b^2\right)\right]^2 =$

$\small = \left[-27a^3b^6+12a^3b^6-8a^2·\dfrac{1}{3}ab^4·\left(-3b^2\right)\right]^2 =$

$\small = \left[-15a^3b^6+\dfrac{\cancel{24}^8}{\cancel3_1}a^3b^6\right]^2 =$

$\small = \left[-15a^3b^6+8a^3b^6\right]^2 =$

$\small = \left[-7a^3b^6\right]^2 =$

$\small = 49a^6b^{12}$