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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 8: 9a^2-1=

Toán Lớp 8:
9a^2-1=

Comments ( 2 )

  1. \text{# Xà Phòng}
    \text{9a² – 1² }
    \text{= (3a)² – 1² }
    \text{(3a -1 ) (3a +1 )}
    \text{⇒ Hằng đẳng thức số 3: A ² – B² = ( A -B )( A + B))}

  2. $\displaystyle \begin{array}{{>{\displaystyle}l}} 9a^{2} -1\\ Sử\ dụng\ hdt\ :a^{2} -b^{2} =( a-b)( a+b) \ \\ 9a^{2} -1\\ =( 3a)^{2} -1^{2}\\ =( 3a-1)( 3a+1) \ \end{array}$

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222-9+11+12:2*14+14 = ? ( )