<em>Answer:</em>
<em>y = - 5 ; x = 6</em>
<em>Step-by-step explanation:</em>
<em>-5y+4x= 49</em>
<em>7y+2x= -23 | × - 2</em>
<em />
<em>-5y+4x= 49</em>
<em>-14y - 4x = 46</em>
<em>___________ +</em>
<em>- 5y - 14y + 4x - 4x = 49 + 46</em>
<em>- 19y = 95 | × - 1</em>
<em>19y = - 95</em>
<em>y = - 95 : 19</em>
<em>y = - 5</em>
<em />
<em>- 5(-5) + 4x = 49</em>
<em>25 + 4x = 49</em>
<em>4x = 49 - 25</em>
<em>4x = 24</em>
<em>x = 24 : 4</em>
<em>x = 6</em>
Answer:
43
Step-by-step explanation:
Answer:
Given that,
The number of grams A of a certain radioactive substance present at time, in years
from the present, t is given by the formula

a) To find the initial amount of this substance
At t=0, we get


We know that e^0=1 ( anything to the power zero is 1)
we get,

The initial amount of the substance is 45 grams
b)To find thehalf-life of this substance
To find t when the substance becames half the amount.
A=45/2
Substitute this we get,


Taking natural logarithm on both sides we get,







Half-life of this substance is 154.02
c) To find the amount of substance will be present around in 2500 years
Put t=2500
we get,




The amount of substance will be present around in 2500 years is 0.000585 grams
X-2 for x=-3
-3-2=-5, add dem negatives