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Vanyuwa [196]
3 years ago
7

Help please

Mathematics
2 answers:
tester [92]3 years ago
6 0

Answer:

64y² - 81

Step-by-step explanation:

(8y +9)(8y - 9)

64y² - 72y + 72y - 81

64y² - 81

tatuchka [14]3 years ago
6 0

<u>Answer:</u>

<h3>. 64y² - 81</h3><h3>. the product is a difference of squares</h3>

<u>Explanation:</u>

(8y + 9)(8y - 9) = 64y² - 81

the product is a difference of squares

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Find the angle between u = i+sqr of 7j and v = -i+9j. Round to the nearest tenth of a degree.
Zolol [24]

\bf ~~~~~~~~~~~~\textit{angle between two vectors } \\\\ cos(\theta)=\cfrac{\stackrel{\textit{dot product}}{u \cdot v}}{\stackrel{\textit{magnitude product}}{||u||~||v||}} \implies \measuredangle \theta = cos^{-1}\left(\cfrac{u \cdot v}{||u||~||v||}\right) \\\\[-0.35em] \rule{34em}{0.25pt}\\\\ \begin{cases} u=i+\sqrt{7}j\implies &\\\\ v=-i+9j\implies & \end{cases} \\\\[-0.35em] ~\dotfill

\bf u\cdot v\implies (1)(-1)~+~(\sqrt{7})(9)\implies -1+9\sqrt{7}\implies 9\sqrt{7}-1~\hfill dot~product \\\\[-0.35em] ~\dotfill\\\\ ||u||\implies \sqrt{1^2+(\sqrt{7})^2}\implies \sqrt{1+7}\implies \sqrt{8}~\hfill magnitudes \\\\\\ ||v||\implies \sqrt{(-1)^2+9^2}\implies \sqrt{1+81}\implies \sqrt{82} \\\\[-0.35em] ~\dotfill

\bf \theta =cos^{-1}\left( \cfrac{9\sqrt{7}-1}{\sqrt{8}\cdot \sqrt{82}} \right)\implies \theta =cos^{-1}\left( \cfrac{9\sqrt{7}-1}{\sqrt{656}} \right) \\\\\\ \theta \approx cos^{-1}(0.8906496638868531)\implies \theta \approx 27.05

make sure your calculator is in Degree mode.

6 0
3 years ago
Una persona pensó hacer una obra en 15 días; pero tardó 10
Ivenika [448]

Answer:

<em>Trabajó 3 horas al día</em>

Step-by-step explanation:

<u>Proporcionalidad</u>

Una persona planeó terminar la obra en 15 dias, pero tardó 10 dias adicionales porque trabajó 2 horas menos por día.

Usaremos proporciones para calcular las horas de trabajo diarias.

Si 2 horas diarias representan 10 dias de atraso, entonces cada hora representa 5 dias de trabajo.

Si la obra tardaba 15 dias, entonces la persona trabajó 15/5 = 3 horas diarias.

8 0
3 years ago
What is greater 17 quarts or 4 gallons?
stepan [7]
17 quarts is greater. 4 gallons is equal to 16 quarts, right?
So 17 quarts would be greater than 4 gallons or 4.25 gallons
17 QUARTS IS GREATER.
5 0
3 years ago
The mean number of words per minute (WPM) typed by a speed typist is 149 with a standard deviation of 14 WPM. What is the probab
Troyanec [42]

Answer:

78.81%

Step-by-step explanation:

We are given;

Population mean; μ = 149

Sample mean; x¯ = 147.8

Sample size; n = 88

standard deviation; σ = 14

Z-score is;

z = (x¯ - μ)/(σ/√n)

Plugging in the relevant values;

z = (147.8 - 149)/(14/√88)

z = -0.804

From z-distribution table attached, we have; p = 0.21186

P(X > 147.8) = 1 - 0.21186 = 0.78814

In percentage gives; p = 78.81%

6 0
2 years ago
Energy is required in order to produce any sound.<br><br> A. True<br> B. False
Vikki [24]

Answer: a. True

Step-by-step explanation:

7 0
3 years ago
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