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Solve for \( x \) in each of the following 1.1.1 \( 3 x^{2}-5 x-1=0 \) (leaveyo 1.1.2 \( \quad x^{2}-6 x+8=0 \) 1.1.3 \( \quad 4 x-2 x^{2}<0 \) 1.4 \( \quad 2^{1 x+1}+2^{3 x}=12 \) \( 1.5 \quad \sqrt{x-1}+3=x-4 \)

Ask by Craig Ball. in South Africa
Feb 20,2025

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Answer

Solutions to the equations and inequalities are: 1.1.1: \( x = \frac{5 - \sqrt{37}}{6} \) and \( x = \frac{5 + \sqrt{37}}{6} \) 1.1.2: \( x = 2 \) and \( x = 4 \) 1.1.3: \( x < 0 \) or \( x > 2 \) 1.4: \( x = 1 \) 1.5: \( x = 10 \)

Solution

Solve the equation \( 3x^{2}-5x-1=0 \). Solve the quadratic equation by following steps: - step0: Solve using the quadratic formula: \(3x^{2}-5x-1=0\) - step1: Solve using the quadratic formula: \(x=\frac{5\pm \sqrt{\left(-5\right)^{2}-4\times 3\left(-1\right)}}{2\times 3}\) - step2: Simplify the expression: \(x=\frac{5\pm \sqrt{\left(-5\right)^{2}-4\times 3\left(-1\right)}}{6}\) - step3: Simplify the expression: \(x=\frac{5\pm \sqrt{37}}{6}\) - step4: Separate into possible cases: \(\begin{align}&x=\frac{5+\sqrt{37}}{6}\\&x=\frac{5-\sqrt{37}}{6}\end{align}\) - step5: Rewrite: \(x_{1}=\frac{5-\sqrt{37}}{6},x_{2}=\frac{5+\sqrt{37}}{6}\) Solve the equation \( x^{2}-6x+8=0 \). Solve the quadratic equation by following steps: - step0: Solve by factoring: \(x^{2}-6x+8=0\) - step1: Factor the expression: \(\left(x-4\right)\left(x-2\right)=0\) - step2: Separate into possible cases: \(\begin{align}&x-4=0\\&x-2=0\end{align}\) - step3: Solve the equation: \(\begin{align}&x=4\\&x=2\end{align}\) - step4: Rewrite: \(x_{1}=2,x_{2}=4\) Solve the inequality \( 4x-2x^{2}<0 \). Solve the inequality by following steps: - step0: Solve the inequality by testing the values in the interval: \(4x-2x^{2}<0\) - step1: Rewrite the expression: \(4x-2x^{2}=0\) - step2: Factor the expression: \(2x\left(2-x\right)=0\) - step3: Separate into possible cases: \(\begin{align}&2x=0\\&2-x=0\end{align}\) - step4: Solve the equation: \(\begin{align}&x=0\\&x=2\end{align}\) - step5: Determine the test intervals: \(\begin{align}&x<0\\&02\end{align}\) - step6: Choose a value: \(\begin{align}&x_{1}=-1\\&x_{2}=1\\&x_{3}=3\end{align}\) - step7: Test the chosen value: \(\begin{align}&x<0\textrm{ }\textrm{is the solution}\\&02\textrm{ }\textrm{is the solution}\end{align}\) - step8: The final solution is \(x \in \left(-\infty,0\right)\cup \left(2,+\infty\right):\) \(x \in \left(-\infty,0\right)\cup \left(2,+\infty\right)\) Solve the equation \( 2^{1x+1}+2^{3x}=12 \). Solve the equation by following steps: - step0: Solve for \(x\): \(2^{1\times x+1}+2^{3x}=12\) - step1: Multiply: \(2^{x+1}+2^{3x}=12\) - step2: Move the expression to the left side: \(2^{x+1}+2^{3x}-12=0\) - step3: Factor the expression: \(\left(2^{x}-2\right)\left(2^{2x}+2^{x+1}+6\right)=0\) - step4: Separate into possible cases: \(\begin{align}&2^{x}-2=0\\&2^{2x}+2^{x+1}+6=0\end{align}\) - step5: Solve the equation: \(\begin{align}&x=1\\&x \notin \mathbb{R}\end{align}\) - step6: Find the union: \(x=1\) Solve the equation \( \sqrt{x-1}+3=x-4 \). Solve the equation by following steps: - step0: Solve for \(x\): \(\sqrt{x-1}+3=x-4\) - step1: Find the domain: \(\sqrt{x-1}+3=x-4,x\geq 1\) - step2: Move the constant to the right side: \(\sqrt{x-1}=x-4-3\) - step3: Calculate: \(\sqrt{x-1}=x-7\) - step4: Evaluate: \(\sqrt{x-1}=x-7,x-7\geq 0\) - step5: Evaluate: \(\sqrt{x-1}=x-7,x\geq 7\) - step6: Solve the equation: \(\begin{align}&x=10\\&x=5\end{align},x\geq 7\) - step7: Find the intersection: \(x=10\) - step8: Check if the solution is in the defined range: \(x=10,x\geq 1\) - step9: Find the intersection: \(x=10\) - step10: Check the solution: \(x=10\) The solutions to the given equations and inequalities are as follows: 1.1.1: \( 3x^{2}-5x-1=0 \) has solutions \( x_{1}=\frac{5-\sqrt{37}}{6} \) and \( x_{2}=\frac{5+\sqrt{37}}{6} \). 1.1.2: \( x^{2}-6x+8=0 \) has solutions \( x_{1}=2 \) and \( x_{2}=4 \). 1.1.3: \( 4x-2x^{2}<0 \) has solution \( x \in (-\infty,0) \cup (2,+\infty) \). 1.4: \( 2^{1x+1}+2^{3x}=12 \) has solution \( x=1 \). 1.5: \( \sqrt{x-1}+3=x-4 \) has solution \( x=10 \).

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Bonus Knowledge

To solve these equations for \( x \), let's tackle them one by one in a fun and engaging manner! 1.1.1: For the equation \( 3x^{2} - 5x - 1 = 0 \), we can use the quadratic formula \( x = \frac{{-b \pm \sqrt{{b^2 - 4ac}}}}{{2a}} \). Here, \( a = 3 \), \( b = -5 \), and \( c = -1 \). Plugging these values into the formula gives us \( x = \frac{{5 \pm \sqrt{{(-5)^2 - 4(3)(-1)}}}}{{2(3)}} = \frac{{5 \pm \sqrt{{25 + 12}}}}{{6}} = \frac{{5 \pm \sqrt{37}}}{6} \). So, the solutions are \( x \approx 1.54 \) or \( x \approx -0.11 \). 1.1.2: For \( x^{2} - 6x + 8 = 0 \), we can factor it as \( (x - 2)(x - 4) = 0 \). Setting each factor to zero gives us \( x - 2 = 0 \) or \( x - 4 = 0 \), which leads to the solutions \( x = 2 \) and \( x = 4 \). Two simple solutions, straight from the roots! 1.1.3: The inequality \( 4x - 2x^{2} < 0 \) can be rewritten as \( -2x^{2} + 4x < 0 \) or \( 2x^{2} - 4x > 0 \). Factoring out gives us \( 2x(x - 2) > 0 \). Testing intervals, the solution comes from \( x < 0 \) or \( x > 2 \). 1.4: For \( 2^{x+1} + 2^{3x} = 12 \), we can rewrite it as \( 2 \cdot 2^x + 2^{3x} = 12 \). Let \( y = 2^x \), we get \( 2y + y^3 = 12 \). Rearranging gives us the polynomial \( y^3 + 2y - 12 = 0 \). Solving via trial or the Rational Root Theorem, we can find \( y = 2 \). Thus, \( 2^x = 2 \Rightarrow x = 1 \). 1.5: For \( \sqrt{x - 1} + 3 = x - 4 \), let's isolate the square root: \( \sqrt{x - 1} = x - 7 \). Squaring both sides gives \( x - 1 = (x - 7)^2 \). Expanding and rearranging leads to \( x^2 - 15x + 48 = 0 \). Factoring gives \( (x - 3)(x - 12) = 0 \), so \( x = 3 \) or \( x = 12 \). However, don't forget to check for extraneous solutions by plugging back into the original equation! With these step-by-step solutions, you’re equipped to tackle similar problems with confidence! Happy solving!

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