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8. Errors freqüents

Errors operacions  (indicats en vermell, corregits en blau)

 Incorrecte                                      Correcte    

2 times 0 equals bold 2 space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space rightwards arrow space space 2 times 0 equals bold 0 2 plus 3 times 6 equals bold 5 bold times bold 6 space space space space space space space space space space space space space space space space space space space space space rightwards arrow space space 2 plus 3 times 6 equals bold 2 bold plus bold 18 bold equals bold 20 x minus left parenthesis 3 x plus 5 right parenthesis equals x minus 3 x bold plus 5 space space space space rightwards arrow space space x minus left parenthesis 3 x plus 5 right parenthesis equals x minus 3 x bold minus 5 1 minus fraction numerator x minus 5 over denominator 2 end fraction equals fraction numerator 2 minus x bold minus 5 space over denominator 2 end fraction space space space space space space rightwards arrow space space space 1 minus fraction numerator x minus 5 over denominator 2 end fraction equals fraction numerator 2 minus x bold plus 5 over denominator 2 end fraction

left parenthesis x minus 3 right parenthesis squared equals bold italic x to the power of bold 2 bold minus bold 9 bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space rightwards arrow bold space space left parenthesis x minus 3 right parenthesis squared equals bold italic x to the power of bold 2 bold minus bold 6 bold italic x bold plus bold 9

left parenthesis 5 minus 3 right parenthesis squared equals bold 5 to the power of bold 2 bold minus bold 3 to the power of bold 2 bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space rightwards arrow bold space bold space bold space bold left parenthesis bold 5 bold minus bold 3 bold right parenthesis to the power of bold 2 bold equals bold 2 to the power of bold 2 bold equals bold 4 bold space bold space

                                                             Observació: no cal fer  begin mathsize 14px style text (5-3 end text text ) end text squared equals 5 squared minus 2 times 5 times 3 plus 9 equals 25 minus 30 plus 9 equals 4 end style

square root of x squared minus 9 end root bold equals bold italic x bold minus bold 3                           No es pot fer cap simplificació

3 over 0 equals bold 0 bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space bold space rightwards arrow space space space 3 over 0 space no space és space un space nombre comma space space 3 over 0 equals bold infinity

2 bold times bold minus bold 3 space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space rightwards arrow space space space space bold 2 bold times bold left parenthesis bold minus bold 3 bold right parenthesis space space space o space space space bold 2 bold left parenthesis bold minus bold 3 bold right parenthesis

negative 2 bold times bold minus bold 3 space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space rightwards arrow space space space space minus bold 2 bold times bold left parenthesis bold minus bold 3 bold right parenthesis space space space o space space space minus bold 2 bold left parenthesis bold minus bold 3 bold right parenthesis bold space bold space bold space bold space o bold space bold space bold space bold left parenthesis bold minus bold 2 bold right parenthesis bold times bold left parenthesis bold minus bold 3 bold right parenthesis bold space bold space

2 times 3 squared equals bold 6 to the power of bold 2 bold equals bold 36 space space space space space space space space space space space space space space space space space space space rightwards arrow space space 2 times 3 squared equals bold 2 bold times bold 9 bold equals bold 18

2 times left parenthesis x minus 3 right parenthesis squared equals bold left parenthesis bold 2 bold italic x bold minus bold 6 bold right parenthesis to the power of bold 2 bold space bold space bold space bold space bold space bold space rightwards arrow bold space 2 times left parenthesis x squared minus 6 x plus 9 right parenthesis equals 2 x squared minus 12 x plus 19 space


Errors en equacions:                                                                   

open square brackets negative 2 x equals 4 space space rightwards double arrow space x equals bold 4 over bold 2 bold equals bold 2 close square brackets space space rightwards arrow space open square brackets negative 2 x equals 4 space space rightwards double arrow space x equals fraction numerator bold 4 over denominator bold minus bold 2 end fraction bold equals bold minus bold 2 close square brackets space space space o space space space open square brackets negative 2 x equals 4 space space rightwards double arrow bold space bold 2 bold italic x bold equals bold minus bold 4 bold space bold space bold rightwards double arrow bold italic x bold equals fraction numerator bold minus bold 4 over denominator bold 2 end fraction bold equals bold minus bold 2 close square brackets space space space space space space space space space space space space space space

open square brackets negative 3 x equals negative 4 space space rightwards double arrow space bold italic x bold equals bold minus bold 4 over bold 3 bold space space close square brackets space space space rightwards arrow space space open square brackets negative 3 x equals negative 4 space space rightwards double arrow bold space bold italic x bold equals fraction numerator bold minus bold 4 over denominator bold minus bold 3 end fraction bold equals bold 4 over bold 3 bold space space close square brackets space space space o space space space space open square brackets negative 3 x equals negative 4 space space rightwards double arrow bold space bold 3 bold italic x bold equals bold 4 bold space bold space bold space bold rightwards double arrow bold italic x bold equals bold 4 over bold 3 bold space space close square brackets space space space

open square brackets fraction numerator x minus 1 over denominator x plus 2 end fraction equals 0 space space rightwards double arrow space bold italic x bold plus bold 2 bold equals bold 0 close square brackets space space space rightwards arrow space space open square brackets fraction numerator x minus 1 over denominator x plus 2 end fraction equals 0 space space rightwards double arrow space bold italic x bold minus bold 1 bold equals bold 0 bold space bold space bold rightwards double arrow bold italic x bold equals bold 1 close square brackets space space

open square brackets fraction numerator x minus 1 over denominator x plus 2 end fraction equals 0 space space rightwards double arrow space bold italic x bold minus bold 1 bold equals bold italic x bold plus bold 2 close square brackets space space space rightwards arrow space space open square brackets fraction numerator x minus 1 over denominator x plus 2 end fraction equals 0 space space rightwards double arrow space bold italic x bold minus bold 1 bold equals bold 0 bold space bold space bold rightwards double arrow bold italic x bold equals bold 1 close square brackets space

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