The answer is actually choice A
---------------------------------------------------------
---------------------------------------------------------
If we add up the equations straight down we will have 0a+2b = 6
Note how adding the 'a' terms gives us 3a + (-3a) = 3a-3a = 0a. The 0a term is really 0 since 0 times anything is 0. So the 'a' terms will go away
The equation 0a+2b = 6 turns into 0+2b = 6 and that simplifies to 2b = 6
To isolate b, we divide both sides by 2
2b = 6
2b/2 = 6/2
b = 3
We can stop here since only one answer choice has b = 3, which is choice A. However, let's keep going to find the value of 'a'
Plug b = 3 into any equation with 'a' and 'b', then solve for 'a'
3a+4b = 9
3a+4*3 = 9
3a+12 = 9
3a+12-12 = 9-12
3a = -3
3a/3 = -3/3
a = -1
So a = -1 and b = 3 pair up to form (a,b) = (-1,3)
--------------------------------------
To check, plug this ordered pair back into both equations
Equation 1:
3a+4b = 9
3*(-1)+4*3 = 9
-3+12 = 9
9 = 9
Equation 1 has been checked out
Equation 2:
-3a-2b = -3
-3(-1)-2(3) = -3
3 - 6 = -3
-3 = -3
this is true as well
So this confirms that the final answer is choice A
3y^-4 × (2y^-4) = 6y^-8
= 6/1/y^8
= 6/y^8
.................................................
1) When x^1 multiply with x^2, 1 will add to 2 and become 3
= x^3
2) y^-1 = 1/y
3^-2 = 1/3^2 = 1/9
5^-2 = 1/5^2 = 1/25
Okay, as you know, adding a positive and a positive gives you a bigger positive number. e.g 21 + 19 = 40.
Subtracting a positive from a positive might give you a negative number or a smaller positive number. e.g 21 - 19 = 2 or 20 - 24 = -4. That's simple, we all learned this! :)
Adding two negatives (e.g -4 + -5) will always give you a negative number. To make it easier, just think of the numbers only (4, 5), add them together, and then just put a negative sign by the answer (e.g 4 + 5 = 9 so put - to make -9).
Subtracting two negatives can be a bit tricky! When we say, for example, -5 - -4, we must turn the negative number that was to the right of the minus ( -4) into a positive number! So now it becomes -5 +4 ! And then you get your answer. (which is -1).
Adding a positive to a negative can give you a positive or a negative answer. It just depends which number is "bigger". E.g -20 + 31. << 31 is the "bigger" number, and it is a positive, so we know that our answer will be positive. E.g -20 + 9. << 20 is the "bigger" number (even though it's a negative but forget about that) and it is negative, so we know that our answer will be negative.
Adding a negative to a positive can give you a negative or a positive answer. Like I said, it depends on which number is "bigger". e.g 20 + -9 . We can just remove the + sign and it now becomes 20 -9, which is easier to understand. 20 is the bigger number, and it is positive, so we get a positive answer. e.g 20 + -30 becomes 20 -30 and -30 is the "bigger" number and it is negative, so we'll get a negative answer.
Subtracting a negative from a positive does the thing I mentioned earlier: e.g 20 - -9. The -9 is right of the minus sign and becomes positive: 20 +9! :)
Subtracting a positive from a negative, like I said, depends on which number is "bigger". e.g -30 - 9 (we know 9 is positive even though we don't show the + sign). Now, to make it simple, just block out the - sign by the 30 so it becomes 30 - 9. You know what that answer is: 21. But because -30 is "bigger", and it is a negative number, the answer will be negative so it's -21. E.g -30 - 42 << Block out the - sign by the 30, and 42 is the "bigger" number, so the answer will be a positive. Just look at the difference between "bigger" number and the smaller number (without signs) . That'll give your answer. 42 - 30 = 12. 42 was the "bigger" number and a positive, and we looked at the difference. :)
