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

Toán Lớp 8: Câu 1: Tính: (2b^2 – 2 – 5b + 6b^3) (3 + 3b^2 – b) Câu 2: Tìm x, biết: (10x^2 – 30x) + (11x – 33) = 0

Toán Lớp 8: Câu 1: Tính:
(2b^2 – 2 – 5b + 6b^3) (3 + 3b^2 – b)
Câu 2: Tìm x, biết:
(10x^2 – 30x) + (11x – 33) = 0

Comments ( 1 )

  1. Giải đáp:
     
    Lời giải và giải thích chi tiết:
    (2b^2-2-5b+6b^3)(3+3b^2-b)
    = 2b^2*3+2b^2*3b^2+2b^2(-b)+(-2)*3+(-2)*3b^2+(-2)(-b)+(-5b)*3+(-5b)*3b^2+(-5b)(-b)+6b^3*3+6b^3*3b^2+6b^3(-b)
    = 2*3b^2+2*3b^2b^2-2b^2b-2*3-2*3b^2+2b-5*3b-5*3b^2b+5b^2+6*3b^3+6*3b^3b^2-6b^3b
    = 18b^5+b^3+5b^2-13b-6
    Câu 2 :
    (10x^2-30x)+(11x-33) = 0
    -> 10x^2 – 19x – 33 = 0
    -> (10x^2+11x)+(-30x-33) = 0
    -> x(10x+11) – 3(10x+11) = 0
    -> (10x+11)(x-3) = 0
    ->\(\left[ \begin{array}{l}10x+11=0\\x-3=0\end{array} \right.\) 
    ->\(\left[ \begin{array}{l}x=-\dfrac{11}{10}\\x=3\end{array} \right.\) 
    Vậy x \in {-11/10,3}

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

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