matematica

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252)

Per esempio poni $a= 4$ e $b=2$ e sostituisci, come segue:

a)

$\dfrac{a+b}{2} \not= \dfrac{a}{2}+b$

$\dfrac{4+2}{2} \not= \dfrac{4}{2}+2$

$\dfrac{6}{2} \not= 2+2$

$3 \not= 4$

b)

$\dfrac{a·b}{2} \not= \dfrac{a}{2}·\dfrac{b}{2}$

$\dfrac{4·2}{2} \not= \dfrac{4}{2}·\dfrac{2}{2}$

$\dfrac{8}{2} \not= 2·1$

$4 \not= 2$

252  

(a+b)/2 ≠ a/2+b 

(a+b)/2 = a/2+b/2 ≠ a/2+b in quanto b/2 ≠ b

(a*b)/2 ≠ a/2*b/2

a/2*b/2 = a*b / 4 ≠ a*b / 2 in quanto 4 ≠ 2

253

a) : (25x+30) / 5 = 5(5x+6) / 5 = 5x+6 

b) : (25x*30) / 5 = 150 x 

c) : (3x*4x*5x*6x) / 18 = 18x^2*20x^2 / 18 = 20x^4 

d) : (5x*6x)-(4x*3x) / 18 = (6(5x*x)-6(2x^2)) / (6*3) = (5x^2-2x^2)/3 = x^2