----- Nội dung ảnh ----- 9. Tìm x biết: a) \( 4x^2 - 36 = 0; \) b) \( 25x^2 - (3x + 1)^2 = 0; \) c) \( x^2 + 12x + 36 = 0; \) d) \( 18x^2 + 12x + 2 = 0; \) e) \( 4x^2 - 4x + 1 = 0; \) f) \( 81x^4 - 18x^2 = -1; \) g) \( x^3 + 6x^2 + 12x + 8 = 0; \) h) \( 8x^3 + 12x^2 + 6x + 2 = 0; \) i) \( 27x^3 - 27x^2 + 9x = 1; \) j) \( 125x^3 - 150x^2 = 9 - 60x; \)
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80 Tham khảo câu trả lời từ Trợ lý ảo Lazi Sure, here are the solutions for the equations: a) \(4x^2 - 36 = 0\) \[4x^2 = 36\] \[x^2 = 9\] \[x = \pm 3\] b) \(25x^2 - (3x + 1)^2 = 0\) \[25x^2 = (3x + 1)^2\] Solve by expanding and equating: \(25x^2 = 9x^2 + 6x + 1\) \[16x^2 - 6x - 1 = 0\] Using the quadratic formula: \[x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\] With \(a = 16\), \(b = -6\), \(c = -1\): \[x = \frac{6 \pm \sqrt{36 + 64}}{32}\] \[x = \frac{6 \pm 10}{32}\] \[x = \frac{16}{32} = \frac{1}{2} \,\, \text{or} \,\, x = \frac{-4}{32} = -\frac{1}{8}\] c) \(x^2 + 12x + 36 = 0\) \((x + 6)^2 = 0\) \[x = -6\] d) \(18x^2 + 12x + 2 = 0\) Using the quadratic formula: \[x = \frac{-12 \pm \sqrt{12^2 - 4 \times 18 \times 2}}{2 \times 18}\] \[x = \frac{-12 \pm \sqrt{144 - 144}}{36}\] \[x = \frac{-12}{36} = -\frac{1}{3}\] e) \(4x^2 - 4x - 1 = 0\) Using the quadratic formula: \[x = \frac{-(-4) \pm \sqrt{(-4)^2 - 4 \times 4 \times (-1)}}{2 \times 4}\] \[x = \frac{4 \pm \sqrt{16 + 16}}{8}\] \[x = \frac{4 \pm \sqrt{32}}{8}\] \[x = \frac{4 \pm 4\sqrt{2}}{8}\] \[x = \frac{1 \pm \sqrt{2}}{2}\] f) \(8x^4 - 18x^2 = -1\) Set it to zero and solve: \[8x^4 - 18x^2 + 1 = 0\] Set \(y = x^2\), solving: \[8y^2 - 18y + 1 = 0\] Use the quadratic formula for \(y\) and back-substitute for \(x\). g) \(x^3 + 6x^2 + 12x + 8 = 0\) Factorization or synthetic division might be useful to simplify. h) \(8x^3 + 12x^2 + 6x + 2 = 0\) Factorization or synthetic division might be useful to simplify. i) \(27x^3 - 27x^2 + 9x = 1\) First move all terms to one side: \[27x^3 - 27x^2 + 9x - 1 = 0\] Factorization or synthetic division might be useful to attempt simplification. j) \(125x^3 - 150x^2 = 9 - 60x\) \[125x^3 - 150x^2 + 60x - 9 = 0\] Try factoring or using numeric/root-solving techniques to get possible real solutions.