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aksik [14]
3 years ago
9

The sum of the digits of a certain two-digit number is 7. Reversing its digits increase the number by 9. What is the number?

Mathematics
2 answers:
Elis [28]3 years ago
5 0
Let the two numbers be x and y.

According to your question;

x + y = 7
10y + x = 10x + y + 9

By equation 1 ; x = 7-y

Substituting the value of x ;

10y + ( 7 -y) = 10(7-y) + y + 9

9y + 7 = 70 -10y + y + 9

9y + 7 = 70 - 9y + 9

=> 18y = 70 -7 + 9
=> 18y = 72
=> y = 4

Substituting for x ;

x = 7 - y
=> x = 7 -4
=> x = 3

Thus, x = 3 and y = 4;
=> The number is 34.
AleksandrR [38]3 years ago
3 0
The original number is <u>34 </u>.
The sum of its digits is (3 + 4) = 7 .
Reversing its digits makes it 43 . . . 9 more than 34.

How I did it:  (There must be a much more elegant mathematical method)

There are only 6 possibilities for the original number.
They are . . .

16
25
34
43
52
61 .

Instead of trying to dream up a sophisticated equation,
I decided it was faster and easier to just go down the list
and look for one that worked. 
The third one I tried worked.
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Answer:

Choice D is correct

Step-by-step explanation:

The first step is to write the polar equation of the conic section in standard form by dividing both the numerator and the denominator by 2;

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The eccentricity of this conic section is thus 1, the coefficient of cos θ. Thus, this conic section is a parabola since its eccentricity is 1.

The value of the directrix is determined as;

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The denominator of the polar equation of this conic section contains (-cos θ) which implies that this parabola opens towards the right and thus the equation of its directrix is;

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Thus, the polar equation represents a parabola that opens towards the right with a directrix located at  x = -3. Choice D fits this criteria

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Will bought 3 college textbooks. One cost 32$, one cost 45$, and one cost 39$. What is the average price of his book?
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Answer:

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Step-by-step explanation:

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Therefore getting our answer of $38.60.


If this helps hit the thank button!

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3 years ago
Which expression is equivalent to 10x2 - (2 – 3x) + (5x - 3x2)?​
djverab [1.8K]
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