Question

rezolvati in R ecuatia (x-3)la a 2 -4(2x+1)=(x-4)(x+4)-7x am nevoie urgent

Answer 1

Răspuns:

Explicație pas cu pas:

( x - 3 )² - 4( 2 x + 1 ) = ( x - 4) ( x + 4) - 7 x

x² - 6 x + 9 - 8 x - 4  = x² - 16 - 7 x

x² - 14 x + 5 = x² - 16 - 7 x

x² - 14 x - x² + 7 x = - 16 - 5

( x² - x² ) + ( - 14 x + 7 x) = - 21

- 7 x = - 21

x = ( - 21) : ( - 7 )

x = 3  ∈ R

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( x-3)² = x² - 2 × x × 3 + ( - 3)² → aplic formula ( a - b)² = a² - 2ab + b²

          = x² - 6 x + 9

- 4(2x+1) = - 8 x - 4 → inmultesc fiecare termen din paranteza cu - 4

( x - 4)(x+ 4) = x² - 4 x + 4 x - 16  = x² - 16

→ aplic formula ( a - b) ( a + b) = a² - b²