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

Toán Lớp 8: câu 1 (x+3).(3x+1),câu 2(2x-3).(4x+5),câu 3(x+5).(x-5)-(3-2x).(x+2) đừng làm tắt nha mn

Toán Lớp 8: câu 1 (x+3).(3x+1),câu 2(2x-3).(4x+5),câu 3(x+5).(x-5)-(3-2x).(x+2) đừng làm tắt nha mn

Comments ( 2 )

  1. $\#Lynn$
    \text{Câu 1:}
    \text{(x+3).(3x+1)}
    =x.3x+x.1+3.3x+3.1
    =3x^2+x+9x+3
    =3x^2+10x+3.
    \text{Câu 2:}
    \text{(2x-3).(4x+5)}
    =2x.4x+2x.5-3.4x-3.5
    =8x^2+10x-12x-15
    =8x^2-2x-15.
    \text{Câu 3:}
    \text{(x+5).(x-5)-(3-2x).(x+2)
    =(x.x+5.x-5.x-5.5)-(3.x+3.2-2x.x-2x.2)
    =x^2+5x-5x-25-3x-6+2x^2+4x)
    =3x^2+x-31.
     

  2. (x+3) (3x+2)
    = 3x^2 + 2x + 9x + 6
    = 3x^2 + 11x + 6
    2) (2x-3) (4x+5) 
    = 8x^2 + 10x – 12x – 15
    = 8x^2 – 2x – 15
    3) (x+5) (x-5) – (3-2x) (x+2)
    = x^2 – 25 – (3x+6-2x^2-4x)
    = x^2 – 25 – 3x – 6 + 2x^2 + 4x
    = 3x^2 + x – 31
     

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

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