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3 years ago

14

Work out the area of this trapezium 6cm 10cm 8cm 17cm

1 answer:

sasho [114]3 years ago

5 0

Answer:

(81√15)/4 ≈ 78.43 cm²

Step-by-step explanation:

It can help to draw a diagram.

The base angle at the side of length 6 can be found using the Law of Cosines. Its opposite side is of length 8, and the two adjacent sides are of length 6 and 7. So, we have ...

8² = 6² +7² -2·6·7·cos(α)

cos(α) = (36+49-64)/(84) = 1/4

α = arccos(1/4) ≈ 75.522°

Then the height of the trapezium is ...

6·sin(75.522°) ≈ 5.80948 . . . . cm

__

The area of the trapezium is given by the formula ...

A = 1/2(b1 +b2)h

A = (1/2)(17 +10)(5.80948) . . . . cm²

A ≈ 78.43 cm²

__

Of course, sin(arccos(1/4)) = (√15)/4, so the exact formulation of the area is ...

A = (81√15)/4 cm²

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2x^3-x^2-3x=210<br> the answer is 5 but I want to know why.

mel-nik [20]

Answer:

$x=5,\frac{-9+\sqrt{255}i }{4} ,\frac{-9-\sqrt{255}i }{4}$

Step-by-step explanation:

1) Move all terms to one side.

$2x^{3} -x^{2} -3x-210=0$

2) Factor $2{x}^{3}-{x}^{2}-3x-210$ using Polynomial Division.

1 - Factor the following.

$2x^{3} -x^{2} -3x-210$

2 - First, find all factors of the constant term 210.

$1,2,3,4,5,6,7,10,14,15,21,30,35,42,70,105,210$

3) Try each factor above using the Remainder Theorem.

Substitute 1 into x. Since the result is not 0, x-1 is not a factor..

$2*1^{3} -1^{2} -3*1-210=-212$

Substitute -1 into x. Since the result is not 0, x+1 is not a factor..

$2(-1)^{3} -(-1)^{2} -3*-1-210=-210$

Substitute 2 into x. Since the result is not 0, x-2 is not a factor..

$2*2^{3} -2^{2} -3*2-210=-204$

Substitute -2 into x. Since the result is not 0, x+2 is not a factor..

$2{(-2)}^{3}-{(-2)}^{2}-3\times -2-210 = -224$

Substitute 3 into x. Since the result is not 0, x-3 is not a factor..

$2\times {3}^{3}-{3}^{2}-3\times 3-210 = -174$

Substitute -3 into x. Since the result is not 0, x+3 is not a factor..

$2{(-3)}^{3}-{(-3)}^{2}-3\times -3-210 = -264$

Substitute 5 into x. Since the result is 0, x-5 is a factor..

$2\times {5}^{3}-{5}^{2}-3\times 5-210 =0$

------------------------------------------------------------------------------------------

⇒ $x-5$

4) Polynomial Division: Divide $2{x}^{3}-{x}^{2}-3x-210$ by $x-5$ .

$2x^{2}$ $9x$ $42$

-------------------------------------------------------------------------

$x-5$ | $2x^{3}$ $-x^{2}$ $-3x$ $-210$

$2x^{3}$ $-10x^{2}$

-----------------------------------------------------------------------

$9x^{2}$ $-3x$ $-210$

--------------------------------------------------------------------------

$42x$ $-210$

$42x$ $-210$

-------------------------------------------------------------------------

5) Rewrite the expression using the above.

$2x^2+9x+42$

$(2x^2+9x+42)(x-5)=0$

3) Solve for $x.$

$x=5$

4) Use the Quadratic Formula.

1 - In general, given $a{x}^{2}+bx+c=0$ , there exists two solutions where:

$x=\frac{-b+\sqrt{b^{2} -4ac} }{2a} ,\frac{-b-\sqrt{b^2-4ac} }{2a}$

2 - In this case, $a=2,b=9$ and $c = 42.$

$x=\frac{-9+\sqrt{9^2*-4*2*42} }{2*2} ,\frac{-9-\sqrt{9^2-4*2*42} }{2*2}$

3 - Simplify.

$x=\frac{-9+\sqrt{255}i }{4} ,\frac{-9-\sqrt{255}i }{4}$

5) Collect all solutions from the previous steps.

$x=5,\frac{-9+\sqrt{255}i }{4} ,\frac{-9-\sqrt{255}i }{4}$

4 0

3 years ago

Read 2 more answers

Mark and Julio are selling flower bulbs for a school fundraiser. Customers can buy bags of windflower bulbs and packages of croc

ikadub [295]

Answer:

Bag of windflower bulbs costs $8.50

Package of crocus bulbs costs $17.60

Step-by-step explanation:

Let $x be the price of one bag of windflower bulbs and $y be the price of one package of crocus bulbs.

1. Mark sold 2 bags of windflower bulbs for $2x and 5 packages of crocus bulbs for $5y. In total he earned $(2x+5y) that is $105. So,

2x+5y=105

2. Julio sold 9 bags of windflower bulbs for $9x and 5 packages of crocus bulbs for $5y. In total he earned $(9x+5y) that is $164.50. So,

9x+5y=164.50

3. You get the system of two equations:

$\left\{\begin{array}{l}2x+5y=105\\ \\9x+5y=164.50\end{array}\right.$

From the first equation

$5y=105-2x$

Substitute it into the second equation:

9x+105-2x=164.50

7x=164.50-105

7x=59.5

x=$8.50

So,

5y=105-2·8.5

5y=105-17

5y=88

y=$17.60

5 0

4 years ago

Write an algebraic expression for the word expression <br> the quotient of c and 8

In-s [12.5K]

Answer:

c/8

Step-by-step explanation:

7 0

4 years ago

In parallelogram ABCD, AB=18. Identify AD. PLEASE HELP ASAP!!

kakasveta [241]

If an is 18 and as is half its length it would be 9, AD = 9

8 0

3 years ago

Helppp<br><br><br> 20x-60/2=10(2x+4)

ikadub [295]

hope it's helpful ❤❤❤❤❤❤

THANK YOU.

7 0

3 years ago