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

Toán Lớp 9: rút gọn : `(a+3)(a+7)+3(a+1)(a+7)-10(a+1)(a+3)`

Toán Lớp 9: rút gọn :
(a+3)(a+7)+3(a+1)(a+7)-10(a+1)(a+3)

Comments ( 2 )

  1. Giải đáp:
    (a+3)(a+7)+3(a+1)(a+7)-10(a+1)(a+3)=-6(a-1)(a+2)
    Lời giải và giải thích chi tiết:
    (a+3)(a+7)+3(a+1)(a+7)-10(a+1)(a+3)
    =a^2+10a+21+3a^2+24a+21-10a^2-40a-30
    =a^2(1+3-10)+a(10+24-40)+(21+21-30)
    =-6a^2-6a+12
    =-6(a^2+a-2)
    =-6(a-1)(a+2)

  2. Giải đáp:
    (a+3)(a+7) + 3(a+1)(a+7)- 10(a+1)(a+3)
    = a^2 + 7a + 3a + 21 + 3(a^2 + 7a + a + 7) – 10(a^2 + 3a + a + 3)
    = a^2 + 7a + 3a + 21 + 3a^2 + 21a + 3a + 21 – 10a^2 – 30a – 10a – 30
    = (a^2 + 3a^2 – 10a^2 ) + (7a + 3a + 21a + 3a – 30a – 10a ) + (21 + 21 – 30)
    = -6a^2 – 6a + 12
    = -6 ( a^2 + a – 2)
    = -6 ( a^2 + 2a – a – 2)
    = -6 [a(a + 2) – (a+2)]
    = -6(a-1)(a+2)

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