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Advanced Math / Nonlinear functions Difficulty: Hard

y = x 2 - 14 x + 22

The given equation relates the variables x and y . For what value of x does the value of y reach its minimum?

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Explanation

The correct answer is 7 . When an equation is of the form y=ax2+bx+c, where a , b , and c are constants, the value of y reaches its minimum when x=-b2a. Since the given equation is of the form y=ax2+bx+c, it follows that a = 1 , b = -14 , and c = 22 . Therefore, the value of y reaches its minimum when x=--1421, or x = 7 .