Simplify each radical expression
1. -\sqrt{20ab^3}
2. \sqrt{2b}\cdot \sqrt{6b}

How do you summarize data in a two-way frequency table?

Arley is building a model of a city map. in one part of the city, three roads form a right triangle, which harley draws as triangle abc, with the following measures: m∠b=90° and m∠a=30°. in his scale model, the hypotenuse of triangle abc, ac¯¯¯¯¯¯¯¯, has a length of 817−−√ cm. what is the value of a (the length of bc¯¯¯¯¯¯¯¯)?

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?