Toán Lớp 6: Tìm x làm từng bước rõ ràng ra: `x ²+x = 3/4`

TRẢ LỜI

1. x^2 + x = 3/4

   => x^2 + x – 3/4 = 0

   => x^2 – 1/2x + 3/2x – 3/4 = 0

   => x . (x – 1/2) + 3/2 . (x – 1/2)  =0

   => (x + 3/2) . (x-1/2) =0

   => x + 3/2 =0 hoặc x-1/2=0

   +) x + 3/2 = 0

   => x = 0 – 3/2

   => x = -3/2

   +)x – 1/2 = 0

   => x = 0 + 1/2

   => x = 1/2

   Vậy x \in{ -3/2 ; 1/2 }

    

   Trả lời
2. Mình giải theo cách lớp 7 nha

   x^2+x=3/4

   ⇒x^2+x-3/4=0

   ⇒x^2+3/2x-1/2x-3/4=0

   ⇒(x^2+3/2x)-(1/2x+3/4)=0

   ⇒x.(x+3/2)-1/2(x+3/2)=0

   ⇒(x-1/2).(x+3/2)=0

   \(⇒\left[ \begin{array}{l}x-\dfrac12=0\\\\x+\dfrac32=0\end{array} \right.\) 

   \(⇒\left[ \begin{array}{l}x=\dfrac12\\\\x=\dfrac{-3}2\end{array} \right.\) 

   Trả lời