Please explain
without using tables or a calculator evaluate

49.2

9

Step-by-step explanation:

7.46² - 2.54² = (7.46 - 2.54)(7.46 + 2.54)

                     = (4.92)(10)

                     = 49.2

(1 x 4) x 3 = [1² + √(1 x 4)] x 3 = [1 + √4] x 3 = [1 + 2] x 3 = 3 x 3 = 9

Y=-2sin((2/7)x)
y = asin(bx+c)+d and the period is given by the equation T = 2/b
where T is the period of the function. "a" changes the amplitude only (vertical stretch). ""c" is the left/right phase shift. "d" moves the whole graph up or down.
The coefficient of x in (2/7)x is 2 pi/7 which would also be equal to b.

T = 2/(2/7) = 7