Question

Tìm x

A) x^2-4x=0

B) 6(x+5)+x^2+5x=0

C) 7x^2+1/2x=0

D) x^2-6x+9=0

Answer 1

a) x^2 - 4x = 0

<=> x^2 = 4x

=> x = 4

Answer 2

hỏi ít thôi

b) = 6(x+5) +x(x+5) = 0

(x+5)(6+x) = 0

x = -5

x = -6

Answer 3

a) x² - 4x = 0

<=> x*(x-4) = 0

<=> x = 0 hoặc x-4 = 0

Nếu x -4 = 0 => x=4

Vậy x =0 hoặc x =4

b) 6(x+5) + x²+ 5x = 0

<=> 6x+30+x²+5x = 0

<=> (6x+x²)+(30+5x) = 0

<=> x(x+6)+5(x+6) = 0

<=>(x+6)(x+5) = 0

<=> x+6=0 hoặc x+5=0

<=>x =-6 hoặc x = -5

Vậy x = -6 hoặc x=-5

c)7x² + 1/2x = 0

<=> x(7x +1/2) = 0

<=> x = 0 hoặc 7x + 1/2 =0

nếu 7x +1/2 = 0 =>7x = -1/2 => x = -1/14

Vậy x = 0 hoặc x =-1/14

d)x² - 6x + 9 = 0

<=> x² - 2.3.x + 3² = 0

<=> (x-3)² = 0

,<=> x -3 = 0

<=> x =3

Vậy x = 3