Question

Giải pt

a. 5x² - 8x + 3 = 0

b. x³ - 7x + 6 = 0

Answer 1

a) 5x² -8x +3 -0

=> 5x² -5x -3x +3 =0

=>5x(x-1) -3(x-1) =0

=> (x-1)(5x -3) =0

=>x-1=0 hoặc 5x-3=0

+ nếu x-1=0 thì x =1

+nếu 5x-3=0 thì 5x=3=>x=3/5

b)x³ -7x +6 =0

=>x³ -x-6x+6 =0

=>x(x² -1)-6(x-1) =0

=>x(x-1)(x+1) -6(x-1) =0

=>(x-1)[x(x+1)-6]=0

=>x-1=0 hoặc x(x+1)-6 =0

+ nếu x -1=0 thì x=1

+nếu  x(x+1)-6 =0 thì x(x+1) =6 => x=2

Answer 2

a.5x² -8x + 3=0

<=>5x² -5x -3x +3=0

<=>(5x²-5x)(3x-3)=0

<=>5x(x-1) - 3(x-1)=0

<=>(x-1)(5x-3)=0

<=>\(\orbr{\begin{cases}x-1=0\\5x-3=0\end{cases}}\)

<=>\(\orbr{\begin{cases}x=1\\x=\frac{3}{5}\end{cases}}\)

b)x³-7x+6=0

<=>x³-x-6x+6=0

<=>(x³-x)-(6x-6)=0

<=>x(x²-1)-6(x-1)=0

<=>x(x+1)(x-1)-6(x-1)=0

<=>(x-1)[x(x+1)-6]=0

<=>\(\orbr{\begin{cases}x-1=0\\x\left(x+1\right)-6=0\end{cases}}\)

<=>\(\orbr{\begin{cases}x=1\\x=\frac{-1}{2}\end{cases}}\)