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Determine all prime numbers a, b and c for which the expression a ^ 2 + b ^ 2 + c ^ 2 - 1 is a perfect square .

kogti [31]

Answer:

The family of all prime numbers such that $a^{2} + b^{2} + c^{2} -1$ is a perfect square is represented by the following solution:

$a$ is an arbitrary prime number. (1)

$b = \sqrt{1 + 2\cdot a \cdot c}$ (2)

$c$ is another arbitrary prime number. (3)

Step-by-step explanation:

From Algebra we know that a second order polynomial is a perfect square if and only if $(x+y)^{2} = x^{2} + 2\cdot x\cdot y + y^{2}$ . From statement, we must fulfill the following identity:

$a^{2} + b^{2} + c^{2} - 1 = x^{2} + 2\cdot x\cdot y + y^{2}$

By Associative and Commutative properties, we can reorganize the expression as follows:

$a^{2} + (b^{2}-1) + c^{2} = x^{2} + 2\cdot x \cdot y + y^{2}$ (1)

Then, we have the following system of equations:

$x = a$ (2)

$(b^{2}-1) = 2\cdot x\cdot y$ (3)

$y = c$ (4)

By (2) and (4) in (3), we have the following expression:

$(b^{2} - 1) = 2\cdot a \cdot c$

$b^{2} = 1 + 2\cdot a \cdot c$

$b = \sqrt{1 + 2\cdot a\cdot c}$

From Number Theory, we remember that a number is prime if and only if is divisible both by 1 and by itself. Then, $a, b, c > 1$ . If $a$ , $b$ and $c$ are prime numbers, then $2\cdot a\cdot c$ must be an even composite number, which means that $a$ and $c$ can be either both odd numbers or a even number and a odd number. In the family of prime numbers, the only even number is 2.

In addition, $b$ must be a natural number, which means that:

$1 + 2\cdot a\cdot c \ge 4$

$2\cdot a \cdot c \ge 3$

$a\cdot c \ge \frac{3}{2}$

But the lowest possible product made by two prime numbers is $2^{2} = 4$ . Hence, $a\cdot c \ge 4$ .

The family of all prime numbers such that $a^{2} + b^{2} + c^{2} -1$ is a perfect square is represented by the following solution:

$a$ is an arbitrary prime number. (1)

$b = \sqrt{1 + 2\cdot a \cdot c}$ (2)

$c$ is another arbitrary prime number. (3)

Example: $a = 2$ , $c = 2$

$b = \sqrt{1 + 2\cdot (2)\cdot (2)}$

$b = 3$

4 0

3 years ago

the problitiy is that a sweet stawberry flavor is 0.8 what is the problity is that a sweet is orang flavor what is anwer

dsp73

Answer:

$\huge\boxed{Answer\hookleftarrow}$

Assuming that there are only 2 flavors of the sweet ⇻ strawberry & orange.

____________________

P (strawberry flavored sweet) = 0.8

P (orange flavored sweet) = ?

____________________

Now, we know that ➳ the value of probability ≤ 1. So, the probability of orange flavored sweets is less than 1.

____________________

So,

P (orange flavored sweet) = 1 - P (strawberry flavored sweet)

P (orange flavored sweet) = $\large\bold{1.0 - 0.8}$

P (orange flavored sweet) = $\large\bold{0.2}$

____________________

✐ The probability that the sweet is orange flavored is 0.2

____________________

ʰᵒᵖᵉ ⁱᵗ ʰᵉˡᵖˢ

# ꧁❣ RainbowSalt2²2² ࿐

4 0

3 years ago

Identify the graph of x^2-8y=0 for theta=90º and write and equation of the translated or rotated graph in general form.

vredina [299]

Answer:

The answer is parabola; (y')² - 8x' = 0 ⇒ answer (b)

Step-by-step explanation:

* At first lets talk about the general form of the conic equation

- Ax² + Bxy + Cy² + Dx + Ey + F = 0

∵ B² - 4AC < 0 , if a conic exists, it will be either a circle or an ellipse.

∵ B² - 4AC = 0 , if a conic exists, it will be a parabola.

∵ B² - 4AC > 0 , if a conic exists, it will be a hyperbola.

* Now we will study our equation:

* x² - 8y = 0

∵ A = 1 , B = 0 , C =

∴ B² - 4AC = (0)² - 4(1)(0) = 0

∵ B² - 4AC = 0

∴ it will be a parabola.

∵ Ф = 90°

* The point (x , Y) will be (x' , y')

∵ x = x'cosФ - y'sinФ and y = x'sinФ + y'cosФ

∵ cos(90) = 0 and sin(90) = 1

∴ x = -y' and y = x'

* lets substitute x and y in the first equation

∴ (-y')² - 8(x') = 0

∴ (y')² - 8x' = 0

* We notice that the x' took the place of y and y' took the place of x

∴ The parabola rotated around the origin by 90°

∴ The equation of the parabola is (y')² - 8x' = 0

* The answer is parabola, with angle of rotation 90°

* The equation is (y')² - 8x' = 0

* Look to the graph

- The blue is x² - 8y = 0

- The green is (y')² - 8x' = 0

7 0

4 years ago

Read 2 more answers

Solve the compound inequality

HACTEHA [7]

Answer:

B

Step-by-step explanation:

3 0

3 years ago

Read 2 more answers

Beveragesat the Store2,000milliliters ofsoda2.5 liters ofapple juice1,500milliliters offruit punch2 liters oflemonade2. Mandy wa

sesenic [268]

Explanation:

The number of Beverages present at the store ;

Soda = 2000ml = 2L

Apple Juice = 2.5L

Fruit Punch = 1.5L

Lemonade = 2L

Now, we have to buy exactly 10 liters but it should be at least one container of each beverage.

Soda + Apple juice + Fruit Punch + Lemonade = 8L

So we need 2 L more.

The only way of doing this is by either having 2 containers of soda or 2 containers of lemonade.

We can conclude that the correct answer is:

Answer:The combination of beverages she can purchase is:Soda = 2 containerApple juice = 1 containerFruit punch= 1 containerLemonade = 1 container

5 0

2 years ago