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Advanced Math / Nonlinear equations in one variable and systems of equations in two variables Difficulty: Medium

7 x 2 - 20 x - 32 = 0

What is the positive solution to the given equation?

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Explanation

The correct answer is 4 . The left-hand side of the given equation can be factored as 7x+8x-4. Therefore, the given equation, 7x2-20x-32=0, can be written as 7x+8x-4=0. Applying the zero product property to this equation yields 7 x + 8 = 0 and x - 4 = 0 . Subtracting 8 from both sides of the equation 7 x + 8 = 0 yields 7 x = - 8 . Dividing both sides of this equation by 7 yields x = - 8 7 . Adding 4 to both sides of the equation x - 4 = 0 yields x = 4 . Therefore, the two solutions to the given equation, 7 x 2 - 20 x - 32 = 0 , are - 8 7 and 4 . It follows that 4 is the positive solution to the given equation.