Find the vertex for this function. f(x)=-2x^2+8x-11

1 answer:

3 0

$\bf \textit{vertex of a vertical parabola, using coefficients} \\\\ f(x)=\stackrel{\stackrel{a}{\downarrow }}{-2}x^2\stackrel{\stackrel{b}{\downarrow }}{+8}x\stackrel{\stackrel{c}{\downarrow }}{-11} \qquad \qquad \left(-\cfrac{ b}{2 a}~~~~ ,~~~~ c-\cfrac{ b^2}{4 a}\right) \\\\\\ \left( -\cfrac{8}{2(-2)}~~,~~-11-\cfrac{8^2}{4(-2)} \right)\implies \left( 2~~,~~-11+\cfrac{64}{8} \right) \\\\\\ (2~~,~~-11+8)\implies (2~~,~~-3)$

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How many triangles and quadrilaterals altogether can be formed using the vertices of a 7-sided regular polygon?

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(E) 70.

Step-by-step explanation: We are given to find the number of triangles and quadrilaterals altogether that can be formed using the vertices of a 7-sided regular polygon.

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$n_t=^7C_3=\dfrac{7!}{3!(7-3)!}=\dfrac{7\times6\times5\times4!}{3\times2\times1\times4!}=35.$