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Solve for \( x \) in the following equations: \( 2^{x}=8 \) \( 3^{x}=81 \) \( 4^{x}=64 \) f) \( 8^{x+5}=4^{2 x+3} \) \( 2^{x}=\frac{1}{4} \) \( 5^{2 x-1}=125 \) h) \( 8^{x-2}=16^{2 x+1} \) h) \( 2^{\frac{3 x+1}{2}}=\frac{1}{16} \)

Ask by Bernard Coleman. in South Africa
Feb 24,2025

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Answer

Here are the solutions for each equation: 1. \( x = 3 \) 2. \( x = 4 \) 3. \( x = 3 \) 4. \( x = 9 \) 5. \( x = -2 \) 6. \( x = 2 \) 7. \( x = -2 \) 8. \( x = -3 \)

Solution

We will solve each equation step‐by‐step by rewriting the numbers as powers of the same base when possible. 1. Equation: 2^x = 8 Recognize that 8 = 2^3. Therefore, 2^x = 2^3, which implies that x = 3. 2. Equation: 3^x = 81 Notice that 81 = 3^4. Hence, 3^x = 3^4, and we have x = 4. 3. Equation: 4^x = 64 Since 64 = 4^3, we immediately deduce that x = 3. (Alternatively, note that 4 = 2^2 and 64 = 2^6, leading to (2^2)^x = 2^6 or 2^(2x) = 2^6, and thus 2x = 6, so x = 3.) 4. Equation: 8^(x+5) = 4^(2x+3) Write 8 and 4 as powers of 2: • 8 = 2^3 • 4 = 2^2 Rewrite the equation: (2^3)^(x+5) = (2^2)^(2x+3) Simplify the exponents: 2^(3(x+5)) = 2^(2(2x+3)) This becomes 2^(3x+15) = 2^(4x+6). Since the bases are the same, set the exponents equal: 3x + 15 = 4x + 6 Solve for x: 15 - 6 = 4x - 3x 9 = x 5. Equation: 2^x = 1/4 Recognize that 1/4 = 4^(–1) and since 4 = 2^2, we have 1/4 = (2^2)^(–1) = 2^(–2). So 2^x = 2^(–2) implies x = –2. 6. Equation: 5^(2x-1) = 125 Write 125 as a power of 5: 125 = 5^3. Therefore, 5^(2x-1) = 5^3. Equate the exponents: 2x – 1 = 3 Solve for x: 2x = 4 x = 2 7. Equation: 8^(x-2) = 16^(2x+1) Express both 8 and 16 in terms of 2: • 8 = 2^3 • 16 = 2^4 Substitute and simplify: (2^3)^(x-2) = (2^4)^(2x+1) This yields: 2^(3(x-2)) = 2^(4(2x+1)) That is: 2^(3x - 6) = 2^(8x + 4) Set the exponents equal: 3x - 6 = 8x + 4 Solve for x: -6 - 4 = 8x - 3x -10 = 5x x = -2 8. Equation: 2^((3x+1)/2) = 1/16 Express 1/16 as a power of 2: 16 = 2^4 so 1/16 = 2^(–4). Now, 2^((3x+1)/2) = 2^(–4). Equate the exponents: (3x + 1)/2 = –4 Multiply both sides by 2: 3x + 1 = –8 Solve for x: 3x = –9 x = –3 Summary of solutions: 1. 2^x = 8   ⟹ x = 3 2. 3^x = 81   ⟹ x = 4 3. 4^x = 64   ⟹ x = 3 4. 8^(x+5) = 4^(2x+3)   ⟹ x = 9 5. 2^x = 1/4   ⟹ x = –2 6. 5^(2x-1) = 125  ⟹ x = 2 7. 8^(x-2) = 16^(2x+1)  ⟹ x = –2 8. 2^((3x+1)/2) = 1/16  ⟹ x = –3

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The Deep Dive

To solve each equation for \( x \): 1. \( 2^{x} = 8 \): Since \( 8 = 2^3 \), we have \( 2^{x} = 2^3 \). Therefore, \( x = 3 \). 2. \( 3^{x} = 81 \): Since \( 81 = 3^4 \), we have \( 3^{x} = 3^4 \). Thus, \( x = 4 \). 3. \( 4^{x} = 64 \): Since \( 64 = 4^3 \), we have \( 4^{x} = 4^3 \). Hence, \( x = 3 \). 4. \( 8^{x+5} = 4^{2x+3} \): We know \( 8 = 2^3 \) and \( 4 = 2^2 \), so we can rewrite the equation as: \[ (2^3)^{x+5} = (2^2)^{2x+3} \Rightarrow 2^{3(x+5)} = 2^{2(2x+3)} \] Equate the exponents: \[ 3(x+5) = 4x + 6 \Rightarrow 3x + 15 = 4x + 6 \Rightarrow x = 9 \] 5. \( 2^{x} = \frac{1}{4} \): Rewrite \( \frac{1}{4} \) as \( 2^{-2} \). Thus, we can say: \[ 2^{x} = 2^{-2} \Rightarrow x = -2 \] 6. \( 5^{2x-1} = 125 \): Since \( 125 = 5^3 \), we have: \[ 5^{2x-1} = 5^3 \Rightarrow 2x - 1 = 3 \Rightarrow 2x = 4 \Rightarrow x = 2 \] 7. \( 8^{x-2} = 16^{2x+1} \): Rewrite both sides using powers of 2: \[ (2^3)^{x-2} = (2^4)^{2x+1} \Rightarrow 2^{3(x-2)} = 2^{4(2x+1)} \] Equate the exponents: \[ 3(x-2) = 4(2x+1) \Rightarrow 3x - 6 = 8x + 4 \Rightarrow -5x = 10 \Rightarrow x = -2 \] 8. \( 2^{\frac{3x+1}{2}} = \frac{1}{16} \): Rewrite \( \frac{1}{16} \) as \( 2^{-4} \): \[ 2^{\frac{3x+1}{2}} = 2^{-4} \Rightarrow \frac{3x+1}{2} = -4 \Rightarrow 3x + 1 = -8 \Rightarrow 3x = -9 \Rightarrow x = -3 \] The solutions for \( x \) are: 1. \( x = 3 \) 2. \( x = 4 \) 3. \( x = 3 \) 4. \( x = 9 \) 5. \( x = -2 \) 6. \( x = 2 \) 7. \( x = -2 \) 8. \( x = -3 \)

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