Answer:
x > -7
Step-by-step explanation:
20 + 8 > -4x
Simplify
28 > -4x
Divide both sides by 4
-28/4 < x
-7 < x
x > -7
To complete the square:
we take the coefficient ox "x" (which in this problem is -20)
we divide it by 2
square that number
then add it to both sides of the equation
-20 / 2 = -10
-10^2 = 100
then we add 100 to both sides of the equation:
x^2 -20x
x^2 -20x +100 = 100
******************************************************
To get the roots of the equation, we take the square root of both sides:
(x -10) * (x-10) = 10
(x-10) = square root (10)
x-10 =
<span>
<span>
<span>
3.1622776602
</span>
</span>
</span>
x1 =
<span>
<span>
<span>
13.1622776602
</span>
and don't forget that square root of 10 also equals </span></span><span><span><span> -3.1622776602
</span>
</span>
</span>
x2 = 10
-<span>
<span>
<span>
3.1622776602
x2 = </span></span></span>
<span>
<span>
<span>
6.8377223398
</span>
</span>
</span>
Answer:
a). 59.049°C
b). 2.1179 seconds
Step-by-step explanation:
Expression representing the final temperature after decrease in temperature of the metal from 100°C to T°C is,
T = 
where x = duration of cooling
a). Temperature when x = 5 seconds
T = 100(0.9)⁵
= 59.049
≈ 59.049°C
b). If the temperature of the metal decreases from 100°C to 80°C
Which means for T = 80°C we have to calculate the duration of cooling 'x' seconds
80 =
0.8 = 
By taking log on both the sides
log(0.8) =log[]
-0.09691 = x[log(0.9)]
-0.09691 = -0.045757x
x = 
x = 2.1179
x ≈ 2.1179 seconds
