Question

Tìm x thỏa mãn: (x+3)(x+4)(x+5)(x+6)=24

Answer 1

khong them viet ct :v

(x + 3)(x + 4)(x + 5)(x + 6) = 24

x^4 + 6x^3 + 5x^3 + 30x^2 + 4x^3 + 24x^2 + 20x^2 + 120x + 3x^2 + 18x^2 + 15x^2 + 90x + 12x^2 + 72x + 60x + 360 = 24

x^4 + 18x^3 + 119x^2 + 342x + 360 = 24

x^4 + 18x^3 + 119x^2 + 342x + 360 - 24 = 0

x^4 + 18x^3 + 119x^2 + 342x + 336 = 0

(x^3 + 16x^2 + 87x + 168)(x + 2) = 0

(x^2 + 9x + 24)(x + 7)(x + 2) = 0

vi x^2 + 9x + 24 # 0 nen:

=> x + 7 = 0 => x = -7

     x + 2 = 0 => x = -2

=> x = -7; -2