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4. Efectuați folosind formulele de calcul prescurtat:
a) (x + 3)(x - 3);
b) (a - 2)(a + 2);
d) (2a + 5b)(2a - 5b); e) (6a + 5)(6a - 5);
g) (8x + 5)(8x - 5);
h) (7x - 3)(7x + 3);
j) (4x +9)(4x - 9);
k) (5x + 6(5x - 6);
c)(b - 4)(b + 4);
f) (5x - 1)(5x + 1);
i) (2x – 3y)(2x + 3y);
1) (3x +8)(3x - 8).

Răspuns :

HawkEyedid

Răspuns:

a) (x + 3)(x - 3) = x² - 9 ;

b) (a - 2)(a + 2) = a² - 4 ;

d) (2a + 5b)(2a - 5b) = 4a² - 25b²;  

e) (6a + 5)(6a - 5) = 36a² - 25 ;  

g) (8x + 5)(8x - 5) = 64x² - 25 ;

h) (7x - 3)(7x + 3) = 49x² - 9 ;

j) (4x +9)(4x - 9) = 16x² - 81 ;

k) (5x + 6(5x - 6) = 25x² - 36;

c)(b - 4)(b + 4) = b² - 16 ;

f) (5x - 1)(5x + 1) = 25x² - 1 ;

i) (2x – 3y)(2x + 3y) = 4x² - 9y² ;

1) (3x +8)(3x - 8) = 9x² - 64 .

Formula de calcul prescurtat in aceste cazuri este :

(a - b)(a + b) = a² - b²

#copaceibrainly

Răspuns: Ai rezolvarea mai jos pentru fiecare subpunct

Explicație pas cu pas:

Salutare!

Folosim formula:

  • (a + b)(a – b) = a² – b²                    
  • a² – b² = (a + b)(a – b)

(a) (x + 3)(x - 3) = x² - 3²

(b) (a - 2)(a + 2) = a² - 2²

(c) (b - 4)(b + 4) = b² - 4² = b² - 16

(d) (2a + 5b)(2a - 5b) = (2a)² - (5b)² = 2²a² - 5²b² = 4a² - 25b²

(e) (6a + 5)(6a - 5) = (6a)² - 5² = 36a² - 25

(g) (8x + 5)(8x - 5) = (8x)² - 5² = 64x² - 25

(h) (7x - 3)(7x + 3) = (7x)² - 3² = 49x² - 9

(j) (4x +9)(4x - 9) = (4x)² - 9² = 16x² - 81

(k) (5x + 6)(5x - 6) = (5x)² - 6² = 25x² - 36

(f) (5x - 1)(5x + 1) =   (5x)² - 1² = 25x² - 1

(i) (2x – 3y)(2x + 3y) =  (2x)² - (3y)² = 4x² - 9y²

(j) (3x +8)(3x - 8) = (3x)² - 8² = 9x² - 64

#copaceibrainly

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