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

Toán Lớp 8: phân tích đa thức thành nhân tử : x mũ 2 – 2xy + y mũ 2 – 25 ab-7b-3a+21 2x mũ 3 + 3x mũ 2 – 1

Toán Lớp 8: phân tích đa thức thành nhân tử :
x mũ 2 – 2xy + y mũ 2 – 25
ab-7b-3a+21
2x mũ 3 + 3x mũ 2 – 1

Comments ( 2 )

  1. x^2 – 2xy + y^2 – 25
    = ( x^2 – 2xy + y^2 ) – 25
    = ( x – y )^2 – 5^2
    = ( x – y – 5 ) ( x – y + 5 )
    ab – 7b – 3a + 21
    = a ( b – 3 ) – 7 ( b + 3 )
    = ( b – 3 ) ( a + 7 )
    2x^3 + 3x^2 – 1
    = 2x^3 – 1x^2 + 4x^2 – 2x + 2x – 1
    = ( 2x – 1 ) x^2 + 2 ( 2x^2 – x ) + 2x – 1 
    = ( 2x – 1 ) x^2 + 2 ( 2x^2 – x ) + 1 ( 2x – 1 )
    = ( 2x – 1 ) x^2 + 2x ( 2x – 1 ) + 1 ( 2x – 1 )
    = ( x^2 + 2x + 1 ) ( 2x – 1 ) 
    = ( x^2 + x + x + 1 ) ( 2x – 1 )  
    =  [ x ( x + 1 ) + x + 1 ] ( 2x – 1 )  
    = ( x + 1 ) ( x + 1 ) ( 2x – 1 )
    =  ( x + 1 )^2 ( 2x – 1 )
     

  2.  +, x^2 – 2xy + y^2 -25
    = (x^2 – 2xy + y^2 ) -25
    = (x-y)^2 – 5^2
    = (x-y+5)(x-y-5)
    +, ab – 7b – 3a + 21
    = (ab-7b) + (-3a +21)
    = b(a-7) – 3(a-7)
    =(a-7)(b-a)
    +, 2x^3 + 3x^2 -1
    = (2x-1)(x^2 + 2x +1)
    = ( x + 1 )^2
    = ( 2x – 1 ) ( x + 1 )^2
     

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

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