Slot method
8 optionns n 1st slot
7 options in 2nd slot (since 1 is at 1st slot)
6 options in 3rd slot
5 options in 4th slot
8*7*6*5=1680 ways
Answer:
The two numbers following 1,-2,3,-4,5... are -6 and 7.
Step-by-step explanation:
index: 1 2 3 4 5 ....
value: 1 -2 3 -4 5
Let the index be n. Then the first term is a(1), the secon is a(2), and so on.
a(2) = 2*(-1)^(2-1) = 2*(-1) = -2 (correct)
a(3) = 3*(-1)^(3-1) = 3*(-1)^2 = 3 (correct)
a(4) = 4*(-1)^(4-1) = 4*(-1)^3 = -4 (correct)
So the general formula for a(n) is: a(n)=n(-1)^(n-1)
Thus,
a(5) = 5(-1)^4 = 5
a(6) = 6(-1)^5 = -6
a(7) = 7(-1)^6 = 7
The "next two numbers in the pattern" are -6 and 7. The first 7 numbers are
1,-2,3,-4,5, -6, 7
Answer: choice 2) SAS
AB = DE is one pair of congruent sides that forms the first S in SAS. The other S in SAS refers to the pair of congruent sides BC = EF. The A in SAS is the angle pair angle B = angle E. Note how angle B and angle E are between the two pairs of congruent sides. The order of the letters matters because SAS is different from SSA, which is not a valid congruence argument. Check out the attached image.
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).
