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

Toán Lớp 8: $(a-b+c)^{2}-(c-b)^{2}+2(a-b+c)$ $(b-c)$ [Tính_nhanh]

Tháng Hai 21, 2023 Toán học 0 Comments 0 views

Toán Lớp 8: $(a-b+c)^{2}-(c-b)^{2}+2(a-b+c)$ $(b-c)$
[Tính_nhanh]

Comments ( 2 )

  1. giangnguyen33
    giangnguyen33
    21 Tháng Hai, 2023 at 4:24 chiều
    Reply
    Chú ý:
    $(A-B)^2=(-B-A)^2=(B-A)^2$
    $(A+B)^2=A^2+2AB+B^2$
    Bài làm:
    $(a-b+c)^2-(c-b)^2+2(a-b+c)(b-c)$
    $= (a-b+c)^2+(b-c)^2+2(a-b+c)(b-c)$
    $= (a-b+c)^2+2(a-b+c)(b-c)+(b-c)^2$
    $= [(a-b+c)+(b-c)]^2$
    $= a^2$

  2. cobelolen
    cobelolen
    21 Tháng Hai, 2023 at 4:24 chiều
    Reply
    (a-b+c)^2 – (c-b)^2 + 2(a-b+c)(b-c)
    = (a-b+c)^2 + (b-c)^2 + 2(a-b+c)(b-c)
    = (a-b+c)^2 + 2(a-b+c)(b-c) + (b-c)^2
    = [(a-b+c) + (b-c)]^2
    = (a – b + c + b -c)^2
    = a^2

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

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