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defon
3 years ago
6

Solve using “completing the square”, thank you! x^4-4x^2+2=0

Mathematics
1 answer:
vodomira [7]3 years ago
7 0

(*)\qquad(a-b)^2=a^2-2ab+b^2\\\\x^4=x^{2\cdot2}=(x^2)^2\\\\x^4-4x^2+2=0\\\\(x^2)^2-4x^2+2=0\\\\\text{substitute}\ t=x^2 > 0\\\\t^2-4t+2=0\\\\t^2-2\cdot t\cdot2+2=0\ \ \ \ \ \ |+2^2\\\\\underbrace{t^2-2\cdot t\cdot2+2^2}_{(*)}+2=2^2\ \ \ \ \ \ |-2\\\\(t-2)^2=4-2\\\\(t-2)^2=2\to t-2=\pm\sqrt2\ \ \ \ \ |+2\\\\t=2-\sqrt2\ \vee\ t=2+\sqrt2\\\\x^2=2-\sqrt2\ \vee\ x^2=2+\sqrt2\\\\x=-\sqrt{2-\sqrt2}\ \vee\ x=\sqrt{2-\sqrt2}\ \vee\ x=-\sqrt{2+\sqrt2}\ \vee\ x=\sqrt{2+\sqrt2}

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a web music store offers two version of a popular song. the size of the standard version is 2.9 megabytes (MB). the size of the
miv72 [106K]

Answer: 260 downloads of the standard version were there.

Step-by-step explanation:

Let x represent the number of downloads of the standard version.

Let y represent the number of downloads of the high-quality version.

Yesterday, the high-quality version downloaded four times as often as the standard version. It means that

y = 4x

The size of the standard version is 2.9 megabytes (MB). the size of the high-quality version is 4.6 MB. the total size downloaded for the two versions was 5538 MB. It means that

2.9x + 4.6y = 5538- - - - - - - - - - - -1

Substituting y = 4x into equation 1, it becomes

2.9x + 4.6 × 4x = 5538

2.9x + 18.4x = 5538

21.3x = 5538

x = 5538/21.3

x = 260

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3 years ago
12. State whether the number 97 is prime, composite, or neither.
Sophie [7]

Answer:

97 is a prime number.

I hope this helps <3


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3 years ago
Find the total surface area of cube whose volume is 27000cm^2
Furkat [3]
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3 years ago
Monday I got 3 papers for each class. I have 7 classes in total. How many papers did I get on Monday.
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7 0
3 years ago
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17. Two tanks are similar in shape. The capacity of the tanks are 1,000,000 litres and 512, 000 liters respectively
Gnesinka [82]

Given that, Two tanks are similar in shape. The capacity of the tanks are 1,000,000 litres and 512, 000 liters respectively.Find the height of the smallest tank if the larger is 300cm tall?

Assume that, the tanks are rectangular in shapes and differ only on their heights. The volume of the larger tank is

V1 = l × w × h1 while the volume of the smaller tank is V2 = l ×w × h2. The ratios of the capacities is

\sf \frac{V1}{V2} = l  \times  w  \times h1  \times  w  \times  h2 =  \frac{h1}{h2}

Solving for the height of the smaller tank h2

\sf \frac{V1}{V2} =  \frac{h1}{h2}

\sf\frac{1000000} {51200} = \frac{ 300 cm }{ h2}

1000000 × h2 = 51200 × 300 cm

h2 = (51200 × 300 cm) /1000000

h2 = 15.36 cm

\sf\implies \: \boxed{ \bf{ \: Height \:  of  \: the \:  smaller  \: tank  \: is  \: 15.36 cm.\: }}

{ \underline {\rule{5000pt}{6pt}}}

5 0
2 years ago
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