31. abcd has area equal to 28 sq. unit. bc is parallel to ad and ba perpendicular to ad. if bc = 6 and ad = 8,
then value of cd =
b.213
a. 2 12
c.4
d. 275

The value of CD is 2√5

Step-by-step explanation:

* Lets describe the figure to know its name

- ABCD is a quadrilateral

∵ BC parallel to AD

∵ BC = 6 units and AD = 8 units

- The quadrilateral which has two parallel sides not equal in length is a

 trapezoid

∴ ABCD is a trapezoid, where BC and AD are its bases

∵ BA perpendicular to AD

∴ BA is the height of the trapezoid

- The area of the trapezoid = 1/2 (base 1 + base 2) × its height

∵ The bases of the trapezoid are BC and AD

∵ BC = 6 and AD = 8

∵ Its area = 28 units²

∴ 1/2 (6 + 8) × height = 28

∴ 1/2 (14) × height = 28

∴ 7 × height = 28 ⇒ divide both sides by 7

∴ height = 4

∵ The height is BA

∴ BA = 4 unit

- To find the length of CD draw a perpendicular line from C to AD and

 meet it at E

∵ BA and CE are perpendicular to AD

∴ BA // CE

∵ BC // AD

- Perpendicular lines between parallel lines are equal in lengths

∴ BA = CE and BC = AE

∵ BA = 4 and BC = 6

∴ CE = 4 and AE = 6

∵ AD = 8 units

∵ AD = AE + ED

∴ 8 = 6 + ED ⇒ subtract 6 from both sides

∴ ED = 2 units

- In ΔCED

∵ m∠CED = 90°

∴ CD = √[(CE)² + (ED)²] ⇒ Pythagoras theorem

∵ CE = 4 and ED = 2

∴ CD = √[(4)² + (2)²] = √[16 + 4] = √20 = 2√5

* The value of CD is 2√5

the range of a function is the range of y-values for which it is defined, or exists. given that we are only looking at the y-values, we can already discount the first two answers as they deal with the domain of the function (range of x-values).

now, what we need to do is find the smallest and highest y-values for which the function is defined. if you'd like, you could take a ruler and start at the very bottom of the graph, find the lowest point, then move the ruler higher and higher until you reach the highest point. doing so either in your head or with an actual ruler, we can see that the lowest y-value is -5 and the highest y-value is -1.

the question now remains as to whether they are included in the range (fourth answer) or excluded (third answer). the key here is to recognise whether they are marked with an open or a closed circle. since both (-2, -5) and (2, -1) are marked with a closed circle, they are points that exist on the graph and are thus included in the range (note that if they were marked with an open circle like (4, -2) then that would signify that there is a break in the graph at that point).

thus, the fourth answer, (y | -5 ≤ y ≤ -1), is correct.

also note that usually it is good practice to scan your eye inbetween the highest and lowest point for any breaks in the graph - we do have one here at (4, -2), however -2 is still included in the range because there is another point that is included in the graph with the same y-value, ie. point (1, -2).

i hope that but if you require any further explanation don't hesitate to comment below.