PLZ HELP TIMED 20 POINTS! WILL MARK BRAINLIEST What is the equation of the graph below?

y = cosine (StartFraction x Over 0.4 EndFraction)
y = cos(5x)
y = cos(0.4x)
y = cosine (StartFraction x Over 5 EndFraction)

What number should be added to both sides of the equation to complete this square? x^2-10x=7

If 1/√5+1/√5+1=p+q√r , find the values of p, q and r

Pyotr tchaikovsky sporting goods operates on a 45% overhead based on the selling price, which results in an overhead of $65.34 on the newest version of an air hockey game set. if the air hockey game set costs pyotr tchaikovsky sports $49.32, find the selling price, the markup, and the net profit.