Answer:
- 2
Step-by-step explanation:
Answer: It has one solution. The solution is (x,y) = (-4,-3)
Add up the equations doing so straight down
x + -x = 0x = 0 so the x terms go away
2y + 2y = 4y
-10 + (-2) = -12
We end up with 4y = -12 so y = -3 after you divide both sides by 4. Use this y value to find the value of x
x+2y = -10
x + 2(-3) = -10
x - 6 = -10
x = -10+6
x = -4
The single solution is (x,y) = (-4,-3)
As a check, plug this solution into each equation to see if you get a true statement or not. Let's do so with the first equation
x+2y = -10
-4 + 2(-3) = -10
-4 - 6 = -10
-10 = -10 .... true
and then the second equation
-x+2y = -2
-(-4) + 2(-3) = -2
4 - 6 = -2
-2 = -2 .... true
both equations are true, so the solution is confirmed
12 - 3 = 9
3 + 9 = 12
12 - 9 = 3
Answer:
18 minutes
Step-by-step explanation:
A = A₀ (½)^(t / T)
where A is the final amount,
A₀ is the initial amount,
t is the time,
and T is the half life.
A = 140 when t = 10. Solve for the half life:
140 = 700 (½)^(10 / T)
0.2 = ½^(10 / T)
log 0.2 = (10 / T) log 0.5
10 / T = 2.32
T = 4.31
When A = 40, t is:
40 = 700 (½)^(t / 4.31)
0.057 = ½^(t / 4.31)
log 0.057 = (t / 4.31) log 0.5
t / 4.31 = 4.13
t = 17.8
Rounded to the nearest whole number, it takes 18 minutes.
Answer:
It was difficult reading the question, as written. Check my assumptions.
Step-by-step explanation:
"five more than the product of two and a number,
decreased by seven"
---
Let the "number" be a.
We are told "five more than . ." means +5,
"the product of two and a number" means 2a,
"decreased by seven" mean -7
Put the statements together to obtain:
+5+2a-7
Simplify to 2a-2
Evaluate when a = 8:
2a-2
2(8)-2
16-2
= 14
