15 = 80% * x
15 = 80/100 * x
15 = 8/10 * x
x = 15 * 10/8
x = 150/8
x = 18.75
<span>80% of 18.75 is </span>15<span>.</span>
Answer:
Step-by-step explanation:
Okay, so I think I know what the equations are, but I might have misinterpreted them because of the syntax- I think when you ask a question you can use the symbols tool to input it in a more clear way, otherwise you can use parentheses and such.
Problem 1:
(x²)/4 +y²= 1
y= x+1
*substitute for y*
Now we have a one-variable equation we can solve-
x²/4 + (x+1)² = 1
x²/4 + (x+1)(x+1)= 1
x²/4 + x²+2x+1= 1
*subtract 1 from both sides to set equal to 0*
x²/4 +x^2+2x=0
x²/4 can also be 1/4 * x²
1/4 * x² +1*x² +2x = 0
*combine like terms*
5/4 * x^2+2x+ 0 =0
now, you can use the quadratic equation to solve for x
a= 5/4
b= 2
c=0
the syntax on this will be rough, but I'll do my best...
x= (-b ± √(b²-4ac))/(2a)
x= (-2 ±√(2²-4*(5/4)*(0))/(2*(5/4))
x= (-2 ±√(4-0))/(2.5)
x= (-2±2)/2.5
x will have 2 answers because of ±
x= 0 or x= 1.6
now plug that back into one of the equations and solve.
y= 0+1 = 1
y= 1.6+1= 2.6
Hopefully this explanation was enough to help you solve problem 2.
Problem 2:
x² + y² -16y +39= 0
y²- x² -9= 0
Answer:
See explanation
Step-by-step explanation:
The standard compound interest formula is 
where:
P is the principal amount
r is the interest rate (typically as a percentage)
t is the time
n is the times compounded per unit of time
So,
1) 
2) 
3) 
You should check my answers though, I may have mixed up some terms.
Roman will have to pay $89.67 for his school supplies.
Since you needed help, I’ll show you my work so you know for next time:
85.40 (.05) = 4.27
85.40 + 4.27
= 89.67
I hope this helps :)
