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natima [27]
2 years ago
8

What is the solution to the equation?  5(8 + 7) = 5 • x + 5 • 7   A. x = 1   B. x = 5   C. x = 7   D. x = 8

Mathematics
1 answer:
Aleks [24]2 years ago
7 0
5(8+7)=5\cdot x+5\cdot7\\\\x=8\\\\Answer:D\\\\5\cdot x+5\cdot7=\underline{5}\cdot x+\underline{5}\cdot7=\underline{5}\cdot(x+7)=5\cdot(8+7)\iff x=8
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A phone company charges $0.06 per minute for local calls and $0.15 per minute for international calls. When your bill comes, it
solmaris [256]
Let's assume two variables x and y which represent the local and international calls respectively. 

x + y = 852 = total number of minutes which were consumed by the company (equation 1)
0.06*x+ 0.15 y =69.84 = total price which was charged for the phone calls (Equation 2)
 from equation 1:-
x=852 -y (sub in equation 2)
0.06 (852 - y) + 0.15 y =69.84

51.12 -0.06 y +0.15 y =69.84 (subtracting both sides by 51.12)
0.09 y =18.74
y= 208 minutes = international minutes (sub in 1) 
208+x=852 (By subtracting both sides by 208)
x = 852-208 = 644 minutes = local minutes
6 0
3 years ago
Numbers that add to -0.5 and multiply to 1
Oliga [24]
Short Answer
There are two numbers
x1 = -0.25 + 0.9682i   <<<< answer 1
x2 = - 0.25 - 0.9582i   <<<< answer 2 
 
I take it there are two such numbers.
Let one number = x
Let one number = y

x + y = -0.5    
y = - 0.5 - x       (1)
xy = 1               (2)

Put equation 1 into equation 2
xy = 1
x(-0.5 - x) = 1
-0.5x - x^2 = 1               Subtract 1 from both sides.
-0.5x - x^2 - 1 = 0          Order these by powers
-x^2 - 0.5x -1 = 0           Multiply though by - 1
x^2 + 0.5x + 1 = 0         Use the quadratic formula to solve this.

\text{x = }\dfrac{ -b \pm \sqrt{b^{2} - 4ac } }{2a}

a = 1
b = 0.5
c = 1


\text{x = }\dfrac{ -0.5 \pm \sqrt{0.5^{2} - 4*1*1 } }{2*1}

x = [-0.5 +/- sqrt(0.25 - 4)] / 2
x = [-0.5 +/- sqrt(-3.75)] / 2
x = [-0.25 +/- 0.9682i

x1 = -0.25 + 0.9682 i
x2 = -0.25 - 0.9682 i

These two are conjugates. They will add  as x1 + x2 = -0.25 - 0.25 = - 0.50.

The complex parts cancel out.  Getting them to multiply to 1 will be a little more difficult. I'll do that under the check.

Check
(-0.25 - 0.9682i)(-0.25 + 0.9682i)
Use FOIL
F:-0.25 * -0.25 = 0.0625
O: -0.25*0.9682i
I: +0.25*0.9682i
L: -0.9682i*0.9682i = - 0.9375 i^2 = 0.9375

Notice
The two middle terms (labled "O" and "I" ) cancel out. They are of opposite signs.

The final result is 0.9375 and 0.0625 add up to 1
 
7 0
3 years ago
Which of the following is a regular quadrilateral
irga5000 [103]

Answer:

(B) square

Step-by-step explanation:

Square (regular quadrilateral): all four sides are of equal length (equilateral), and all four angles are right angles.

8 0
2 years ago
Read 2 more answers
Complete the comparison: 5+4= ?
qaws [65]
Complete the comparison: 5+4=? =9
6 0
3 years ago
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Find the value of x that makes the equation true<br> 3 ( x- 8 ) + 2x = 76
vovikov84 [41]

Answer:

x = 20

Step-by-step explanation:

3 (x-8) +2x = 76

3x - 24 +2x = 76

3x+2x = 76+24

5x = 100

x = 20

7 0
2 years ago
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