(D) The sum of the first three terms of an arithmetic sequence is 36 and their product is 1140. Determine the three terms.
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Let the first term of the arithmetic sequence be \( a \), and the common difference be \( d \). Therefore, the first three terms can be expressed as \( a \), \( a + d \), and \( a + 2d \). According to the problem: 1. The sum of the three terms is given by: \[ a + (a + d) + (a + 2d) = 3a + 3d = 36 \] This simplifies to: \[ a + d = 12 \quad (1) \] 2. The product of the three terms is given by: \[ a(a + d)(a + 2d) = 1140 \] Substituting \( d = 12 - a \) from equation (1) into the product gives us: \[ a(a + (12 - a))(a + 2(12 - a)) = 1140 \] Simplifying this: \[ a(12)(24 - a) = 1140 \] This expands to: \[ 12a(24 - a) = 1140 \] Dividing both sides by 12: \[ a(24 - a) = 95 \] This leads to the quadratic equation: \[ a^2 - 24a + 95 = 0 \] 3. To find \( a \), we can use the quadratic formula: \[ a = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{24 \pm \sqrt{576 - 380}}{2} = \frac{24 \pm \sqrt{196}}{2} = \frac{24 \pm 14}{2} \] This yields two potential solutions for \( a \): \[ a = \frac{38}{2} = 19 \quad \text{or} \quad a = \frac{10}{2} = 5 \] 4. Now we can find \( d \) for both values: - If \( a = 19 \): \[ d = 12 - 19 = -7 \] The terms would then be \( 19, 12, 5 \). - If \( a = 5 \): \[ d = 12 - 5 = 7 \] The terms would then be \( 5, 12, 19 \). Thus, the three terms of the arithmetic sequence are \( 5, 12, 19 \).