Question

[Huỳnh Ngọc Nhiên]

Tìm x biết :

(x - 2)³ - (x - 3)(x² + 3x + 9) + 6(x + 1)² = 49

x(x + 5)(x - 5) - (x + 2)(x² - 2x + 4) = 42

(x + 3)³-(x + 1)³ = 56

Answer 1

[Minh Triều]

(x - 2)³ - (x - 3)(x² + 3x + 9) + 6(x + 1)² = 49

<=>x³-6x²+12x-8-(x³-27)+6(x²+2x+1)=49

<=>x³-6x²+12x-8-x³+27+6x²+12x+6=49

<=>24x+25=49

<=>24x=24

<=>x=1

x(x + 5)(x - 5) - (x + 2)(x² - 2x + 4) = 42

<=>x(x²-25)-(x³+8)=42

<=>x³-25x-x³-8=42

<=>-25x-8=42

<=>-25x=50

<=>x=-2

Answer 2

[Nguyễn Ngân]

2 nha !!!

k nha !!!