Question

Tìm x : 

a. x⁴ - 10x³ + 25x² = 0

b. x³ + 3x² + 3x + 1 =0

Answer 1

a) x⁴ - 10x³ + 25x² = (x²)² - 2.x².5x + (5x)² = (x² - 5x)² = 0 => x(x - 5) = 0 => x = 0 hay x - 5 = 0 => x = 0 ; 5

b) x³ + 3x² + 3x + 1 = x³ + 3.x².1 + 3.x.1² + 1³ = (x + 1)³ = 0 => x + 1 = 0 => x = -1

Answer 2

a,x^2(x^2-10x+25)=0

x^2(x-5)^2=0

=> x^2=0 hoac (x-5)^2=0

=>x=0 hoac 5

Answer 3

b,x^3+3x^2+3x+1=0

(x+1)^3=0

=> x+1=0

=>x=-1