All categories

2 years ago

If a = 5+2√6 then find a²-1÷a²

Mathematics

1 answer:

Umnica [9.8K]2 years ago

5 0

Answer:

a²+1/a² = 7

Step-by-step explanation:

Given, a = (3+√5)/2

We have to find the value of a² + 1/a².

1/a = 1/((3+√5)/2) = 2/(3+√5)

By taking conjugate,

2/(3+√5) = 2/(3+√5) × (3-√5)/(3-√5)

= 2(3-√5) / (3+√5)(3-√5)

By using algebraic identity,

(a - b)(a + b) = a² - b²

(3+√5)(3-√5) = (3)² - (√5)²

= 9 - 5

= 4

2(3-√5) / (3+√5)(3-√5) = 2(3-√5) / 4

So, 1/a = (3-√5)/2

Now, a² = [(3+√5)/2]²

= (3+√5)²/4

By using algebraic identity,

(a + b)² = a² + 2ab + b²

(3+√5)² = (3)² + 2(3)(√5) + (√5)²

= 9 + 6√5 + 5

= 14 + 6√5

a² = (14+6√5)/4

= 2(7+3√5)/4

a² = (7+3√5)/2

Now, 1/a² = [(3-√5)/2]²

= (3-√5)²/4

By using algebraic identity,

(a - b)² = a² - 2ab + b²

(3-√5)² = (3)² - 2(3)(√5) + (√5)²

= 9 - 6√5 + 5

= 14 - 6√5

1/a² = (14-6√5)/4

1/a² = (7-3√5)/2

a²+1/a² = (7+3√5)/2 + (7-3√5)/2

= 7/2 + 3√5/2 + 7/2 - 3√5/2

= 7/2 + 7/2

= 7

Therefore, a²+1/a² = 7

You might be interested in

Find the sum of the given polynomials. ax + by + c, 2ax - 3by + c, and by - c

Sedbober [7]

The answer is 3ax -by + c hope this helps

4 0

3 years ago

A candle is 9 inches long. Ronnie lights the candle and records the height of the candle, y inches, for x hours.

DochEvi [55]

In the future, please post the full problem with all included instructions. After doing a quick internet search, I found your problem listed somewhere else. It mentions two parts (a) and (b)

Part (a) asked for the equation of the line in y = mx+b form

That would be y = -2x+9

This is because each time y goes down by 2, x goes up by 1. We have slope = rise/run = -2/1 = -2. This indicates that the height of the candle decreases by 2 inches per hour. The slope represents the rate of change.

The initial height of the candle is the y intercept b value. So we have m = -2 and b = 9 lead us from y = mx+b to y = -2x+9

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

Part (b) then asks you to graph the equation. Because this is a linear equation, it produces a straight line. We only need 2 points at minimum to graph any line. Let's plot (0,9) and (1,7) on the same xy grid. These two points are the first two rows of the table. Plot those two points and draw a straight line through them. The graph is below

7 0

2 years ago

Explain why 1+1=2 ?

Evgen [1.6K]

DUDE WHAT GRADE R U IN!?!?!? IT'S SIMPLE ADDITION , BRO!!!

4 0

3 years ago

Explain how to solve linear equations.

muminat

Answer:

that means you need to find the surface area, but not the part that is touching the ground or the bottom.

3 0

3 years ago

P= 3in <br> a) find the length of each side of the square<br> b) find the area of the square

Anna007 [38]

Step-by-step explanation:

what does P mean ?

I assume it is perimeter ?

what is the perimeter of a square ?

come on, there is practically nothing in math that is easier to solve.

a square has 4 equal sides.

so, to go one time around the whole square, we have to go along every one of its 4 sides (which are all of equal length).

so, when I get the perimeter number, I know this is the result of all 4 sides added together.

and how can we express having 4 times the same number ? exactly how we say it in English : 4 times the number.

therefore

P = 4 × side length

and from there we can immediately deduct

side length = P / 4 = 3/4 in

now we know how long the sides of the square are.

what is the area of the square ?

like for any rectangle the area is length×width. just that length=width, so that we end up with length×length = length².

therefore, the area is

3/4 × 3/4 = (3/4)² = 9/16 in²

this is important : a length is measured e.g. in inches (in). an area is then measured in square-inches = in²

3 0

3 years ago