Question

[Lê Phương Linh]

tìm x

a/ 4x²+8x+3=0

b/ (2x+3)²=(x-6)²

c/ x³-7x²+15x-9=0

Answer 1

[Moon Light]

a)4x²+8x+3=0

<=>(4x²+2x)+(6x+3)=0

<=>2x(2x+1)+3(2x+1)=0

<=>(2x+1)(2x+3)=0

<=>2x+1=0 hoặc 2x+3=0

<=>x=-1/2 hoặc x=-3/2

b)(2x+3)²=(x-6)²

<=>(2x+3)²-(x-6)²=0

<=>(2x-3-x+6)(2x+3+x-6)=0

<=>(x+3)(3x-3)=0

<=>x+3=0 hoặc 3x-3=0

<=>x=-3 hoặc x=1

c)x³-7x²+15x-9=0

<=>(x³-6x²+9x)-(x²-6x+9)=0

<=>x(x-3)²-(x-3)²=0

<=>(x-3)²(x-1)=0

<=>(x-3)²=0 hoặc x-1=0

<=>x=3 hoặc x=1