1.tính nhanh a,(24x^5-9x^3+18x^2):3x b(-4x^2+x^3-20+5x):(x-4) 2.tinh a,(7.3^5-3^4+3^6):3^4 b,(16^3-64^2):8^3

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1. Giải thích các bước giải:

    Ta có:

   \(\begin{array}{l}
   1,\\
   a,\\
   \left( {24{x^5} – 9{x^3} + 18{x^2}} \right):3x\\
    = \left[ {3x\left( {8{x^4} – 9{x^2} + 6x} \right)} \right]:3x\\
    = 8{x^4} – 9{x^2} + 6x\\
   b,\\
   \left( { – 4{x^2} + {x^3} – 20 + 5x} \right):\left( {x – 4} \right)\\
    = \left[ {\left( {{x^3} – 4{x^2}} \right) + \left( {5x – 20} \right)} \right]:\left( {x – 4} \right)\\
    = \left[ {{x^2}\left( {x – 4} \right) + 5\left( {x – 4} \right)} \right]:\left( {x – 4} \right)\\
    = \left[ {\left( {x – 4} \right)\left( {{x^2} + 5} \right)} \right]:\left( {x – 4} \right)\\
    = {x^2} + 5\\
   2,\\
   \left( {{{7.3}^5} – {3^4} + {3^6}} \right):{3^4}\\
    = \left[ {{3^4}.\left( {7.3 – 1 + {3^2}} \right)} \right]:{3^4}\\
    = 7.3 – 1 + {3^2}\\
    = 21 – 1 + 9\\
    = 29\\
   b,\\
   \left( {{{16}^3} – {{64}^2}} \right):{8^3}\\
    = \left[ {{{\left( {2.8} \right)}^3} – {{\left( {{8^2}} \right)}^2}} \right]:{8^3}\\
    = \left[ {{2^3}{{.8}^3} – {8^4}} \right]:{8^3}\\
    = \left( {{{8.8}^3} – {8^4}} \right):{8^3}\\
    = 0:{8^3}\\
    = 0
   \end{array}\)

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