Question

a,(x^2-2x+4)(x+2)-x(x-1)(x+1)+3=0        b,(x-1)(3-2x)+(2x-1)(x+3)=4
c,(x+1)(3x^2+x-2)-x^2(3x+4)=5   d,(xy+1)(x^2y^2-xy+1)+(x^3-1)(1-y^3)=x^3+y^3

Answer 1

a) (x² - 2x + 4)(x + 2) - x(x - 1)(x + 1) + 3 = 0

x³ + 8 - x(x² - 1) + 3 = 0

x³ + 8 - x³ + x + 3 = 0

x + 11 = 0

x = -11

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

3x - 2x² - 3 + 2x + 2x² + 6x - x - 3 = 4

10x - 6 = 4

10x = 4 + 6

10x = 10

x = 10 : 10

x = 1

c) (x + 1)(3x² + x - 2) - x²(3x + 4) = 5

3x³ + x² - 2x + 3x² + x - 2 - 3x³ - 4x² = 5

-x - 2 = 5

-x = 5 + 2

-x = 7

x = -7

d) (xy + 1)(x²y² - xy + 1) + (x³ - 1)(1 - y³) = x³ + y³

= (xy)³ + 1 + x³ - x³y³ - 1 + y³ = x³ + y³

x³ + y³ = x³ + y³

x³ + y³ - x³ - y³ = 0

0x + 0y = 0 (luôn đúng với mọi x, y thuộc R)