<h3><em>
Answer: </em></h3><h3><em> I think the first answer is S(t) = 2^t - 1 .</em>
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An ordered pair (x,y) is a solution to a system of equations if it makes all the equations true.
Let's check whether (–1, 5) makes the equations true.
Plugging –1 in the first equation for x and 5 in for y, we get
–1 + 5 = 4: TRUE
Plugging –1 in the second equation for x and 5 in for y, we get
–1 – 5 = –6: TRUE
Since it makes both the equations true, it's a solution to the system of equations. So the answer choice is D, the 4th one.
12. Answer: 2130
<u>Step-by-step explanation:</u>
T = -0.01y + 10.6
9.2 = -0.01y + 10.6
<u>-10.6</u> <u> -10.6 </u>
-1.4 = -0.01y
<u> ÷-0.01</u> <u>÷-0.01 </u>
140 = y
"y" represents the number of years after 1990
1990 + 140
= 2130
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13. Answer: -0.0036° per foot
<u>Step-by-step explanation:</u>
Since the relationship is linear, then we can set up the values as x, y coordinates and use the slope formula to find the rate of degrees over feet.
(6562, 63) and (16405, 28)
rate = 
= 
= 
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14. Answer: $0.28 per kWh
<u>Step-by-step explanation:</u>
Same reason as #13
(200, 55) and (500, 140)
rate = 
= 
= 
X^2+ (y+8)^2 = 81.....this is C.
X^2 + y^2 + 16y +64=81 so x^2 + y^2 + 16y = 17.....this is D.
So I’d say C and D are correct