Answer:
5
10
4
7
Step-by-step explanation:
Apply the value of x into the expressions: 
3(5) - 10 = 15 - 10 
            = 5
5² - 15 = 25 - 15
           = 10
5(5) - 21 = 25 - 21
              = 4
5 + 10 - 8 = 15 - 8
                = 7 
 
        
                    
             
        
        
        
2cosx=2sin2x. Sin2x is an identity for 2sinxcos. So 2[2sinxcosx] gives you 4sinxcosx. 2cosx=4sinxcosx. Divide 2cosx on both sides and gives you 2sinx=0 and divide again, sinx=0. Sinx is 0 at 0 and 360 degrees, or pi and 2pi. So thats what x would be. 0,360,pi,2pi.
        
             
        
        
        
Answer:
y = 5
Step-by-step explanation:
Since this is an isosceles triangle, Angle B and Angle C are equivalent. We can use this to find x
3x = 75
x = 25
Angles in a triangle add up to 180, so knowing the measure of Angle B and Angle C, we can find the measure of Angle A
Angle A = 180-(75+75)
Angle A = 180-150
Angle A = 30
We know Angle A = 4y+10
4y + 10 = 30
4y = 20
y = 5
 
        
             
        
        
        
Answer:
Step-by-step explanation:
10+6n=n-5
6n-n=-5-10
5n=-15
n=-3
 
        
             
        
        
        
Answer:
because they allow us to make direct comparisons 
Step-by-step explanation: