----- Nội dung ảnh ----- Bài 5. Tìm x, biết: 1. \((x + 2)^2 - x(x + 3) = 2\) 2. \((x + 2)(x - 2) - (x + 1)^2 = 7\) 3. \(6x - (2x + 1)(3x + 2) + 3 = 0\) 4. \((x + 3)(x + 1) - (x - 1)(2x + 1) = 0\) 5. \((x + 1)^2 + (x - 9)(x - 3) - (x - 7)^2 = 0\) 6. \((x - 2)(x + 3)(x + 2)(x - 3) + x^4 = 0\) 7. \((x + 2)(x - 3) - (x^2 - x + 1) = 23\)
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50 Tham khảo câu trả lời từ Trợ lý ảo Lazi Sure, let's solve each equation one by one. 1. \((x + 2)^2 - x(x + 3) = 2\) 2. \((x + 2)(x - 2) - (x + 1)^2 = 7\) 3. \(6x - (2x + 1)(3x + 2) + 3 = 0\) 4. \((x + 3)(x + 1) - (x - 1)(2x + 1) = 0\) 5. \((x + 1)^2 + (x - 9)(x - 3) - (x - 7)^2 = 0\) 6. \((x - 2)(x + 3)(x + 2)(x - 3) + x^4 = 0\) 7. \((x + 2)(x - 3) - (x^2 - x + 1) = 23\) Now, we'll solve each equation: 1. \((x + 2)^2 - x(x + 3) = 2\) Expanding the terms, we have: \[ (x^2 + 4x + 4) - (x^2 + 3x) = 2 \] Simplifying: \[ x + 4 = 2 \] So, \( x = -2 \). 2. \((x + 2)(x - 2) - (x + 1)^2 = 7\) Expand and simplify: \[ (x^2 - 4) - (x^2 + 2x + 1) = 7 \] Further simplification gives: \[ -2x - 5 = 7 \] \[ -2x = 12 \] \[ x = -6 \] 3. \(6x - (2x + 1)(3x + 2) + 3 = 0\) Expanding the terms: \[ 6x - (6x^2 + 4x + 3x + 2) + 3 = 0 \] \[ 6x - 6x^2 - 7x - 2 + 3 = 0 \] \[ -6x^2 - x + 1 = 0 \] This is a quadratic equation. We can solve using the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] \[ x = \frac{-(-1) \pm \sqrt{(-1)^2 - 4(-6)(1)}}{2(-6)} \] \[ x = \frac{1 \pm \sqrt{1 + 24}}{-12} \] \[ x = \frac{1 \pm \sqrt{25}}{-12} \] \[ x = \frac{1 \pm 5}{-12} \] \[ x = \frac{-6}{-12} \quad \text{or} \quad x = \frac{-4}{-12} \] \[ x = \frac{1}{2} \quad \text{or} \quad x = \frac{1}{3} \] 4. \((x + 3)(x + 1) - (x - 1)(2x + 1) = 0\) Expanding the terms: \[ (x^2 + 4x + 3) - (2x^2 + x - 2x - 1) = 0 \] \[ x^2 + 4x + 3 - 2x^2 - 1 = 0 \] \[ -x^2 + 4x + 2 = 0 \] Solving a quadratic equation: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] \[ x = \frac{-4 \pm \sqrt{16 + 8}}{-2} \] \[ x = \frac{-4 \pm \sqrt{24}}{-2} \] \[ x = \frac{-4 \pm 2\sqrt{6}}{-2} \] \[ x = 2 \pm \sqrt{6} \] 5. \((x + 1)^2 + (x - 9)(x - 3) - (x - 7)^2 = 0\) Expand each term: \[ (x^2 + 2x + 1) + (x^2 - 3x - 9x + 27) - (x^2 - 14x + 49) = 0 \] \[ x^2 + 2x + 1 + x^2 - 12x + 27 - x^2 + 14x - 49 = 0 \] \[ x^2 + 4x - 21 = 0 \] Solve this quadratic equation using the quadratic formula: \[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \] \[ x = \frac{-4 \pm \sqrt{16 + 84}}{2} \] \[ x = \frac{-4 \pm \sqrt{100}}{2} \] \[ x = \frac{-4 \pm 10}{2} \] \[ x = 3 \quad \text{or} \quad x = -7 \] 6. \((x - 2)(x + 3)(x + 2)(x - 3) + x^4 = 0\) Notice that \((x - 2)(x + 2)\) and \((x + 3)(x - 3)\) are differences of squares: \[ ((x^2 - 4)(x^2 - 9)) + x^4 = 0 \] \[ x^4 - 13x^2 + 36 + x^4 = 0 \] \[ 2x^4 - 13x^2 + 36 = 0 \] Let \(y = x^2\), then the equation becomes: \[ 2y^2 - 13y + 36 = 0 \] Solve this quadratic equation: \[ y = \frac{13 \pm \sqrt{169 - 288}}{4} \] \[ y = \frac{13 \pm \sqrt{-119}}{4} \] Since the discriminant is negative, there are no real solutions. 7. \((x + 2)(x - 3) - (x^2 - x + 1) = 23\) Expand and simplify: \[ (x^2 - 3x + 2x - 6) - (x^2 - x + 1) = 23 \] \[ x^2 - x - 6 - x^2 + x - 1 = 23 \] \[ -7 = 23 \] Since this simplifies to a false statement, there is no solution for this equation. These are the solutions for each given equation.