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

Toán Lớp 8: (5 -x).(5+ x)=? Giúp vssssssssssss

Toán Lớp 8: (5 -x).(5+ x)=?
Giúp vssssssssssss

Comments ( 2 )

  1. C1
    (5-x)(5+x)
    =5(5+x)-x(5+x)
    =25+5x-5x+x^2
    =25+x^2
    ____________________________
    C2
    (5-x)(5+x)
    =(5)^2-x^2
    =25-x^2
    Hằng đẳng thức: A^2-B^2=(A+B)(A-B)

  2. (5-x).(5+x)
    =5^2-x^2
    =25-x^2
    Giải thích:
    Áp dụng hằng đẳng thức:
    a^2-b^2=(a-b)(a+b).

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