Answer:
2520cm²
Step-by-step explanation:
Surface area = sum of the area of all the bases.
Area of bottom base = 28 * 30 = 840
Area of right base = 25 * 30 = 750
Area of left base = 17 * 30 = 510
Area of two triangles = ( 15 * 28 ) / 2 = 210 * 2 = 420
Then add all the areas together to find surface area
Surface area = 840 + 750 + 510 + 420 = 2520cm²
Relevant Formulas:
Area of a rectangle = length * width. This formula was used to find the area of the bottom base, the right base and the left base
Area of a triangle = ( height * base length ) / 2 . This formula was used to find the area of the sides which are triangles.
Complete the square.


Use de Moivre's theorem to compute the square roots of the right side.


Now, taking square roots on both sides, we have


Use de Moivre's theorem again to take square roots on both sides.



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:<span> </span><span>You need to know the derivative of the sqrt function. Remember that sqrt(x) = x^(1/2), and that (d x^a)/(dx) = a x^(a-1). So (d sqrt(x))/(dx) = (d x^(1/2))/(dx) = (1/2) x^((1/2)-1) = (1/2) x^(-1/2) = 1/(2 x^(1/2)) = 1/(2 sqrt(x)).
There is a subtle shift in meaning in the use of t. If you say "after t seconds", t is a dimensionless quantity, such as 169. Also in the formula V = 4 sqrt(t) cm3, t is apparently dimensionless. But if you say "t = 169 seconds", t has dimension time, measured in the unit of seconds, and also expressing speed of change of V as (dV)/(dt) presupposes that t has dimension time. But you can't mix formulas in which t is dimensionless with formulas in which t is dimensioned.
Below I treat t as being dimensionless. So where t is supposed to stand for time I write "t seconds" instead of just "t".
Then (dV)/(d(t seconds)) = (d 4 sqrt(t))/(dt) cm3/s = 4 (d sqrt(t))/(dt) cm3/s = 4 / (2 sqrt(t)) cm3/s = 2 / (sqrt(t)) cm3/s.
Plugging in t = 169 gives 2/13 cm3/s.</span>