First, you need to isolate the x in the first equation.
-x + 5y = 1
Subtract 5y from both sides, leaving you with the following equation:
-x = 1-5y
Because you are trying to solve for positive x and not negative x, you need to make x positive. Therefore you divide both sides by -1. In Algebra, when 1 is the coefficient of the variable, it is not shown, but it is still there. The new equation will be the following: x = 5y-1
Now you just need to substitute the x within the second equation for the x equation we just solved for.
Therefore, the right answer will be 2(5y-1)+4y= -4. Now, all you have to do is choose the answer that states exactly that, which is the first choice.
Use the exponential function of f(x)= 100x times (1.08)^2
Let the number be n.
Then:
n^2 + (1/n)^2 = 82/9; find n. Find the LCD; it is 9n^2.
Mult all 3 terms by 9n^2:
82*9n^2
9n^4 + 9 = (82/9)(9n^2) => 9n^4 + 9 = ------------
9
Then 9n^4 - 82n^2 + 9 = 0
I used my graphing calculator to find that n = 3.
Let's check: is 3^2 + (1/3)^2 = 82/9?
Is 9 + 1/9 = 82/9?
Is 81 + 1 = 82? YES. So, n=3 is a solution.