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3 years ago

Solve the equation by completing the square. Round to the nearest hundredth if necessary x^2+3x=25

Mathematics

2 answers:

Citrus2011 [14]3 years ago

7 0

Answer:

The solutions are: $x= 3.72, -6.72$

Step-by-step explanation:

$x^2+ 3x = 25\\ \\ x^2+3x+(\frac{3}{2})^2 = 25 +(\frac{3}{2})^2\\ \\ (x+\frac{3}{2})^2 = 25+\frac{9}{4}\\ \\ (x+\frac{3}{2})^2 =27.25\\ \\ \sqrt{(x+\frac{3}{2})^2} =\pm \sqrt{27.25} \\ \\ x+1.5= \pm \sqrt{27.25} \\ \\ x= -1.5 \pm \sqrt{27.25}\\ \\ x=-1.5+ \sqrt{27.25}=3.72015... \approx 3.72\\ \\ or\\ \\ x=-1.5-\sqrt{27.25} =-6.72015...\approx -6.72$

So, the solutions are: $x= 3.72, -6.72$

Lilit [14]3 years ago

6 0

X=-3/2 plus or minus to the square root 109/2

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Looking at the top of tower A and base of tower B from points C and D, we find that ∠ACD = 60°, ∠ADC = 75° and ∠ADB = 30°. Let t

katrin2010 [14]

Answer:

$\text{Exact: }AB=25\sqrt{6},\\\text{Rounded: }AB\approx 61.24$

Step-by-step explanation:

We can use the Law of Sines to find segment AD, which happens to be a leg of $\triangle ACD$ and the hypotenuse of $\triangle ADB$ .

The Law of Sines states that the ratio of any angle of a triangle and its opposite side is maintained through the triangle:

$\frac{a}{\sin \alpha}=\frac{b}{\sin \beta}=\frac{c}{\sin \gamma}$

Since we're given the length of CD, we want to find the measure of the angle opposite to CD, which is $\angle CAD$ . The sum of the interior angles in a triangle is equal to 180 degrees. Thus, we have:

$\angle CAD+\angle ACD+\angle CDA=180^{\circ},\\\angle CAD+60^{\circ}+75^{\circ}=180^{\circ},\\\angle CAD=180^{\circ}-75^{\circ}-60^{\circ},\\\angle CAD=45^{\circ}$

Now use this value in the Law of Sines to find AD:

$\frac{AD}{\sin 60^{\circ}}=\frac{100}{\sin 45^{\circ}},\\\\AD=\sin 60^{\circ}\cdot \frac{100}{\sin 45^{\circ}}$

Recall that $\sin 45^{\circ}=\frac{\sqrt{2}}{2}$ and $\sin 60^{\circ}=\frac{\sqrt{3}}{2}$ :

$AD=\frac{\frac{\sqrt{3}}{2}\cdot 100}{\frac{\sqrt{2}}{2}},\\\\AD=\frac{50\sqrt{3}}{\frac{\sqrt{2}}{2}},\\\\AD=50\sqrt{3}\cdot \frac{2}{\sqrt{2}},\\\\AD=\frac{100\sqrt{3}}{\sqrt{2}}\cdot\frac{ \sqrt{2}}{\sqrt{2}}=\frac{100\sqrt{6}}{2}={50\sqrt{6}}$

Now that we have the length of AD, we can find the length of AB. The right triangle $\triangle ADB$ is a 30-60-90 triangle. In all 30-60-90 triangles, the side lengths are in the ratio $x:x\sqrt{3}:2x$ , where $x$ is the side opposite to the 30 degree angle and $2x$ is the length of the hypotenuse.

Since AD is the hypotenuse, it must represent $2x$ in this ratio and since AB is the side opposite to the 30 degree angle, it must represent $x$ in this ratio (Derive from basic trig for a right triangle and $\sin 30^{\circ}=\frac{1}{2}$ ).

Therefore, AB must be exactly half of AD:

$AB=\frac{1}{2}AD,\\AB=\frac{1}{2}\cdot 50\sqrt{6},\\AB=\frac{50\sqrt{6}}{2}=\boxed{25\sqrt{6}}\approx 61.24$

3 0

3 years ago

Read 2 more answers

Find the sum of -6/ab + a^2/b^2

Ymorist [56]

Answer:

$\frac{1}{ab^{2} }$ (a³ - 6b)

Step-by-step explanation:

$\frac{-6}{ab} + \frac{a^{2} }{b^{2} }$

= $\frac{-6b + a^{3} }{ab^{2} }$

= $\frac{1}{ab^{2} }$ (a³ - 6b)

4 0

3 years ago

HELP I NEED HELP ASAP

Crazy boy [7]

Answer:

<u><em>C. strong negative</em></u>

Step-by-step explanation:

The reason why is because, the student's grade is falling dramatically while they watch TV. So therefore, we can erase A and D. B maybe however, it isn't "weak" but it is a heavy decrease. Therefore, your answer would be C.

5 0

3 years ago

Solve with elimination

Fittoniya [83]

I'm pretty sure this is correct

4 0

3 years ago

If $5,000 is borrowed with an interest of 12.3% compounded semi-annually, what is the total amount of money needed to pay it bac

jarptica [38.1K]

Answer:

$7153.03

Step-by-step explanation:

To find the total amount after 3 years, we can use the formula for compound tax:

P = Po * (1+r/n)^(t*n)

where P is the final value, Po is the inicial value, r is the rate, t is the amount of time and n depends on how the tax is compounded (in this case, it is semi-annually, so n = 2)

For our problem, we have that Po = 5000, r = 12.3% = 0.123, t = 3 years and n = 2, then we can calculate P:

P = 5000 * (1 + 0.123/2)^(3*2)

P = 5000 * (1 + 0.0615)^6

P = $7153.029

Rounding to the nearest cent, we have P = $7153.03

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3 years ago