The second step is wrong. What should've been done is to find greatest common factor (gcf) of 1/6 and -2. This is because you cannont add together a number with a variable to a number without a variable. So get the variable by itself by subtracting 1/6 from both sides.
1/5x + 1/6 = -2
___— 1/6_— 1/6
____________
Turn -2 into a fraction and find the gcf of -2 and 6:
1/5x + 1/6 = -2
___— 1/6_— 1/6
____________
1/5x = -2/1 — 1/6 ——> 1/5x = -12/6 — 1/6
1/5x = -13/6
Then divide each side by 1/5 to get the variable by itself; remeber: when dividing a fraction by a fraction, you multiply by the reciprocal.
5/1 • 1/5x = -13/6 • 5/1
x = 65/6
Then, simplify
65/6} 10.83 or 10 83/100
According to my calculations the theoretical answer about to be given is number c
4.74/.06=79
19.44/.54=36
I used a calculator. You can change each decimal into a fraction to solve too.
20x+30y= c(total cost of money)
Part B: 20(10)+5(30)
200+150=$350
You do the implcit differentation, then solve for y' and check where this is defined.
In your case: Differentiate implicitly: 2xy + x²y' - y² - x*2yy' = 0
Solve for y': y'(x²-2xy) +2xy - y² = 0
y' = (2xy-y²) / (x²-2xy)
Check where defined: y' is not defined if the denominator becomes zero, i.e.
x² - 2xy = 0 x(x - 2y) = 0
This has formal solutions x=0 and y=x/2. Now we check whether these values are possible for the initially given definition of y:
0^2*y - 0*y^2 =? 4 0 =? 4
This is impossible, hence the function is not defined for 0, and we can disregard this.
x^2*(x/2) - x(x/2)^2 =? 4 x^3/2 - x^3/4 = 4 x^3/4 = 4 x^3=16 x^3 = 16 x = cubicroot(16)
This is a possible value for y, so we have a point where y is defined, but not y'.
The solution to all of it is hence D - { cubicroot(16) }, where D is the domain of y (which nobody has asked for in this example :-).
(Actually, the check whether 0 is in D is superfluous: If you write as solution D - { 0, cubicroot(16) }, this is also correct - only it so happens that 0 is not in D, so the set difference cannot take it out of there ...).
If someone asks for that D, you have to solve the definition for y and find that domain - I don't know of any [general] way to find the domain without solving for the explicit function).
