Arectangle has an area of 126 m2 and a width of 7 m. what is its length?

126 divided by 7 equals 18

18 m

To find the length divide the area by the width 

126/7= 18

check your work to make sure 18 is the length 

18*7= 126

Since 18 * 7 does equal 126, 18 is your answer :)

There's no real formulas here; it's mostly just understanding.for a function f, ⇒ where the first derivative f' is positive is where  f is increasing. ⇒ where  the first derivative f' is negative is where  f is decreasing.⇒ where the second derivative f'' is positive is where f is concave up.  ⇒ where the second derivative f'' is negative is where f is concave down.⇒ the second derivative is the derivative of the first derivative; in other words, it is  the rate of change of the first derivative======(1a)f is increasing at x = 2 since the first derivative is positive at x = 2.f is concave down at x = 2 since the second derivative is negative at x = 2.(1b)we expect f(2.1) to be greater than -3. -3 was the value of f at x = 2 since f is increasing at x = 2, we would expect the function's value to increase from that value.  (1c)we expect f'(2.1) to be less than 1.5. 1.5 was the value of f' at x = 2. the second derivative f' is negative x = 2. since the 2nd derivative is the rate of change of the 1st derivative, this means that the 1st derivative is decreasing at x = 2. thus, we expect f'(2.1) to be less than 1.5(1d)sketch a graph where the point at (3,-2) is increasing but concave down.concave down has a general shape of a frownindicate that the slope of the tangent line to f at x = 2 is 1.5 (rise of 1.5, run of 1)