Solve 2cos^2x + cosx − 1 = 0 for x over the interval [0, 2 π ).
a.π and π/3
b.π, π/3, and 5π/3
c.1 and 2π/3
d.1, 2π/3, and 4π/3
e.1, π/3, and 5π/3

The parabola x = y² - 9 opens: a.)up b.)down c.) right d.)left

Is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis.

Atriangular field has sides of lengths 21, 39, and 41 yd. find the largest angle. (round your answer to the nearest degree.)