(2x+1) ² – (x-1) ² ; 9(x+5) ² – (x-7) ; 49(y-4) ² -9 (y+2) ²

0 bình luận về “(2x+1) ² – (x-1) ² ; 9(x+5) ² – (x-7) ; 49(y-4) ² -9 (y+2) ²”

1. Đáp án:

   $\begin{array}{l}
   a){\left( {2x + 1} \right)^2} – {\left( {x – 1} \right)^2}\\
   = \left( {2x + 1 – x + 1} \right)\left( {2x + 1 + x – 1} \right)\\
   = 3x.\left( {x + 2} \right)\\
   b)kiem\,tra\,lai\,de\,nhe\\
   c)\,49{\left( {y – 4} \right)^2} – 9{\left( {y + 2} \right)^2}\\
   = {\left[ {7\left( {y – 4} \right)} \right]^2} – {\left[ {3\left( {y + 2} \right)} \right]^2}\\
   = {\left( {7y – 28} \right)^2} – {\left( {3y + 6} \right)^2}\\
   = \left( {7y – 28 – 3y – 6} \right)\left( {7y – 28 + 3y + 6} \right)\\
   = \left( {4y – 34} \right)\left( {10y – 22} \right)
   \end{array}$

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