Help me with this question

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

Need asap. solve for the following inequality

Which equation shows the quadratic formula used correctly to solve 5x2 + 3x -4 0 for x? cos -3+ v (3) 2-4() 2(5) 3+ |(3)² +4() 205) 3+ (3) 2-4() -3+ v (3)² +4()