Toán Lớp 8: tìm x: 2x^2-x-6=0 (4x-1)^2-9=0

Question

Toán Lớp 8:  tìm x:  2x^2-x-6=0             (4x-1)^2-9=0

thanhbinh2k5 · Answer

2x^{2}-x-6=0   $ Leftrightarrow$ (2x^{2}-4x)+(3x-6)=0   $ Leftrightarrow$ 2x(x-2)+3(x-2)=0   $ Leftrightarrow$ (x-2)(2x+3)=0   $ Leftrightarrow$  ( left[  begin{array}{l}x-2=0  2x+3=0 end{array}  right. )    $ Leftrightarrow$  ( left[  begin{array}{l}x=2  x=- dfrac{3}{2} end{array}  right. )    $ text{Vậy}$ S={2;-3/2}   -------------------------------------------------   (4x-1)^{2}-9=0   $ Leftrightarrow$ (4x-1-3)(4x-1+3)=0   $ Leftrightarrow$ (4x-4)(4x+2)=0   $ Leftrightarrow$  ( left[  begin{array}{l}4x-4=0  4x+2=0 end{array}  right. )    $ Leftrightarrow$  ( left[  begin{array}{l}x=1  x=- dfrac{1}{2} end{array}  right. )    $ text{Vậy}$ S={1;-1/2}

cobexinhdep · Answer

Giải đáp + Lời giải và giải thích chi tiết: 2x^{2}-x-6=0 <=>(2x^{2}-4x)+(3x-6)=0 <=>2x(x-2)+3(x-2)=0 <=>(x-2)(2x+3)=0 <=> ( left[ begin{array}{l}x-2=0 2x+3=0 end{array} right. ) <=> ( left[ begin{array}{l}x=2 x=- dfrac{3}{2} end{array} right. ) Vậy S={2;-3/2} (4x-1)^{2}-9=0 <=>(4x-1-3)(4x-1+3)=0 <=>(4x-4)(4x+2)=0 <=> ( left[ begin{array}{l}4x-4=0 4x+2=0 end{array} right. ) <=> ( left[ begin{array}{l}x=1 x=- dfrac{1}{2} end{array} right. ) Vậy S={1;-1/2}