Which of the equations are true identities? A. N ( n − 2 ) ( n + 2 ) = n 3 − 4 n B. ( x + 1 ) 2 − 2 x + y 2 = x 2 + y 2 + 1

Both A and B are true identities

Step-by-step explanation:

A. N ( n − 2 ) ( n + 2 ) = n 3 − 4 n

We need to show that (left-hand-side)L.H.S = R.H.S (right-hand-side)

So,

 n ( n − 2 ) ( n + 2 ) = n(n² - 2²)     (difference of two squares)

                               = n³ - 2²n       (expanding the brackets)

                               = n³ - 4n         (simplifying)

So,                L.H.S  = R.H.S

B. ( x + 1 )² − 2x + y² = x² + y² + 1

We need to show that (left-hand-side)L.H.S = R.H.S (right-hand-side)

So,

( x + 1 )² − 2x + y² = x² + 2x + 1 - 2x + y²   (expanding the brackets)

                             = x² + 2x - 2x + 1  + y²   (collecting like terms)

                             = x² + 1 + y²        

                             = x² + y² + 1                    (re-arranging)

So,              L.H.S  = R.H.S

So, both A and B are true identities since we have been able to show that L.H.S  = R.H.S in both situations.

55.44 inches

step-by-step explanation:

part a. assuming a perfectly linear relationship, we can find the slope from the first two data points.

slope = m = (change in rainfall)/(change in years)

= (61.80 -62.33)/(2005 -2004) = -0.53/1 = -0.53

then the point-slope form of the equation of the line can be written as

y = m(x -h) +k . . . . . m = -0.53, (h, k) = (0, 62.33)

y = -0.53x +62.33 . . . x = years after 2004

part b. in 2017, x = 2017 -2004 = 13. then the predicted rainfall is

y = -0.53·13 +62.33 = 55.44 . . inches

the predicted rainfall in 2017 is 55.44 in.