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2 years ago

Is the solution of this equation extraneous?

Mathematics

2 answers:

UkoKoshka [18]2 years ago

6 0

Answer:

x = - 3 is extraneous

Step-by-step explanation:

Given

$\sqrt{x+7}$ - 1 = x ( add 1 to both sides )

$\sqrt{x+7}$ = x + 1 ( square both sides )

x + 7 = (x + 1)² ← distribute right side

x + 7 = x² + 2x + 1 ( subtract x + 7 from both sides )

0 = x² + x - 6 ← in standard form

0 = (x + 3)(x - 2) ← in factored form

Equate each factor to zero and solve for x

x + 3 = 0 ⇒ x = - 3

x - 2 = 0 ⇒ x = 2

As a check

Substitute these values into the equation and if both sides are equal then they are the solutions.

x = - 3 : $\sqrt{-3+7}$ - 1 = $\sqrt{4}$ - 1 = 2 - 1 = 1 ≠ - 3

x = 2 : $\sqrt{2+7}$ - 1 = $\sqrt{9}$ - 1 = 3 - 1 = 2

x = 2 is a solution and x = - 3 is extraneous

Katarina [22]2 years ago

6 0

Good morning ☕️

____________________

Step-by-step explanation:

Look at the photo below for the answer.

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An acute triangle has sides measuring 10 cm and 16 cm. The length of the third side is unknown.

saveliy_v [14]

Answer: Choice B

12.5 < x < 18.9

================================================

Explanation:

We have a triangle with these side lengths:

a = 10
b = 16
c = x = unknown

Let's assume that b = 16 is the largest side of this triangle.

By the converse of the pythagorean theorem, we need $b^2 < a^2+c^2$ to be true in order for an acute triangle to happen.

So,

$b^2 < a^2 + c^2\\\\c^2 > b^2 - a^2\\\\c > \sqrt{b^2-a^2}\\\\x > \sqrt{16^2-10^2}\\\\x > \sqrt{156}\\\\x > 12.4899959967968 \ \text{(approximate)}\\\\x > 12.5$

Now let's consider the possibility that the missing side x is actually the longest side.

Using the same theorem as before, we would say,

$c^2 < a^2 + b^2\\\\c < \sqrt{a^2 + b^2}\\\\x < \sqrt{10^2 + 16^2}\\\\x < \sqrt{356}\\\\x < 18.8679622641132 \ \text{(approximate)}\\\\x < 18.9\\\\$

We found that x > 12.5 and x < 18.9

This is the same as saying 12.5 < x and x < 18.9

Put together, they form the approximate answer of 12.5 < x < 18.9

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2 years ago

A university law school accepts 2 out of every 5 applicants. If the school accepted 180 students, find how many applications the

Lubov Fominskaja [6]

You can set up rations to do this.
So we know that they accept 2:5.
So It would be 180: 450.

8 0

2 years ago

Find the area of a triangle b=72.5 a=105 c=64

riadik2000 [5.3K]

There are two methods I know. hope it'd help :)

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2 years ago

A home improvement contractor is painting the walls and ceiling of a rectangular room. The volume of the room is 875.00 cubic fe

Reika [66]

Answer:

The room dimensions for a minimum cost are: sides of 10 feet and height of 8.75 feet.

Step-by-step explanation:

We have a rectangular room with sides x and height y.

The volume of the room is 875 cubic feet, and can be expressed as:

$V=x^2y=875$

With this equation we can define y in function of x as:

$x^2y=875\\\\y=\dfrac{875}{x^2}$

The cost of wall paint is $0.08 per square foot. We have 4 walls which have an area Aw:

$A_w=xy=x\cdot \dfrac{875}{x^2}=\dfrac{875}{x}$

The cost of ceiling paint is $0.14 per square foot. We have only one ceiling with an area:

$A_c=x^2$

We can express the total cost of painting as:

$C=0.08\cdot (4\cdot A_w)+0.14\cdot A_c\\\\C=0.08\cdot (4\cdot \dfrac{875}{x})+0.14\cdot x^2\\\\\\C=\dfrac{280}{x}+0.14x^2$

To calculate the minimum cost, we derive this function C and equal to zero:

$\dfrac{dC}{dx}=280(-1)\dfrac{1}{x^2}+0.14(2x)=0\\\\\\-\dfrac{280}{x^2}+0.28x=0\\\\\\0.28x=\dfrac{280}{x^2}\\\\\\x^3=\dfrac{280}{0.28}=1000\\\\\\x=\sqrt[3]{1000} =10$

The sides of the room have to be x=10 feet.

The height can be calculated as:

$y=875/x^2=875/(10^2)=875/100=8.75$

The room will have sides of 10 feet and a height of 8.75 feet.

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3 years ago

6th grade math , help me please :)

svet-max [94.6K]

Answer:

The correct answer is A. 3/5

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3 years ago