(x+2)^2=9*(x^2-4*x+4) 4*(2*x+7)-9*(x+3)^2=0 15/07/2021 Bởi Alice (x+2)^2=9*(x^2-4*x+4) 4*(2*x+7)-9*(x+3)^2=0
(x + 2)² = 9(x² – 4x + 4) ⇔ x² + 4x + 4 = 9x² – 36x + 36 ⇔ x² + 4x + 4 – 9x² + 36x – 36 = 0 ⇔ -8x² + 40x – 32 = 0 ⇔ -8(x² – 5x + 4) = 0 ⇒ x² – 5x + 4 = 0 ⇔ x² – 4x – x + 4 = 0 ⇔ x(x – 4) – (x – 4) = 0 ⇔ (x – 4)(x – 1) = 0 ⇔ \(\left[ \begin{array}{l}x-4=0\\x-1=0\end{array} \right.\) ⇔ \(\left[ \begin{array}{l}x=4\\x=1\end{array} \right.\) Vậy x = 4 hoặc x = 1 ___________________________ 4(2x + 7)² – 9(x + 3)² = 0 ⇔ [2(2x + 7) – 3(x + 3)] . [2(2x + 7) + 3(x + 3)] = 0 ⇔ (4x + 14 – 3x – 9) . (4x + 14 + 3x + 9) = 0 ⇔ (x + 5) . (7x + 23) = 0 ⇔ \(\left[ \begin{array}{l}x+5=0\\7x+23=0\end{array} \right.\) ⇔ \(\left[ \begin{array}{l}x=-5\\x=\frac{-23}{7}\end{array} \right.\) Vậy x = -5 hoặc x = `\frac{-23}{7}` Bình luận
(x + 2)² = 9(x² – 4x + 4)
⇔ x² + 4x + 4 = 9x² – 36x + 36
⇔ x² + 4x + 4 – 9x² + 36x – 36 = 0
⇔ -8x² + 40x – 32 = 0
⇔ -8(x² – 5x + 4) = 0
⇒ x² – 5x + 4 = 0
⇔ x² – 4x – x + 4 = 0
⇔ x(x – 4) – (x – 4) = 0
⇔ (x – 4)(x – 1) = 0
⇔ \(\left[ \begin{array}{l}x-4=0\\x-1=0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=4\\x=1\end{array} \right.\)
Vậy x = 4 hoặc x = 1
___________________________
4(2x + 7)² – 9(x + 3)² = 0
⇔ [2(2x + 7) – 3(x + 3)] . [2(2x + 7) + 3(x + 3)] = 0
⇔ (4x + 14 – 3x – 9) . (4x + 14 + 3x + 9) = 0
⇔ (x + 5) . (7x + 23) = 0
⇔ \(\left[ \begin{array}{l}x+5=0\\7x+23=0\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=-5\\x=\frac{-23}{7}\end{array} \right.\)
Vậy x = -5 hoặc x = `\frac{-23}{7}`
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