Toán Lớp 8: giải phương trình ( chi tiết ) :
-2x^2 + 8x – 3 = 0
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Toán Lớp 8: giải phương trình ( chi tiết ) :
-2x^2 + 8x – 3 = 0
Comments ( 2 )
-2x^2+8x-3 =0⇔ -2x^2 + 2.4x -8 +5=0⇔ -2( x^2 -4x +4 )+5=0⇔ -2.( x^2-2.x.2+2^2 )+5=0 ⇔ -2( x – 2 )^2 +5=0⇔ -2( x – 2 )^2 = -5⇔ ( x – 2 )^2 = $\frac{-5}{-2}$ ⇔ ( x – 2 )^2 = $\frac{5}{2}$⇔ ( x – 2 )^2 – $\dfrac{5}{2}$ =0⇔ ( x – 2 )^2 -$\sqrt[2]{(\frac{x}{y}) }$$^{2}$ =0⇔ ( x – 2 – $\sqrt{(\frac{5}{2}) }$ ).( x – 2 +$\sqrt{(\frac{5}{2}) }$ ) =0⇒ \(\left[ \begin{array}{l} x – 2 -\sqrt{(\frac{5}{2})} =0\\x – 2 +\sqrt{(\frac{5}{2} } )=0\end{array} \right.\) ⇔ \(\left[ \begin{array}{l}x =2 +\sqrt{(\frac{5}{2}) }\\x = 2 – \sqrt{(\frac{5}{2}) } \end{array} \right.\) .