Anyone good with Algebra?

Question

1. Simplify: - [2a - 5(3a - 4)]

2. Solve for r.
S =
a
___(fraction line)
l - r

3. Solve: 8a - (2a - 8) = 2(4a - 1)

4. Solve: 3(a - 6) - 4(1 - 2a)a = 8a^2

Please explain and tell which number you're explaining. Thank you

Answer 1

1. Simplify: - [2a - 5(3a - 4)]
-(2a - 15a + 20)
-(-13a +20)
13a + 20

2. Solve for r.
S = a/(l - r)
(L-r)S = A
SL - SR = A
SR = SL - A
R = (SL - A) / S

3. Solve: 8a - (2a - 8) = 2(4a - 1)
2a + 8 = 8a -3
11 = 6a
a = 11/6

4. Solve: 3(a - 6) - 4(1 - 2a)a = 8a^2
3a - 18 - 4a + 8a^2 = 8a^2
-a = 18
a = -18

Answer 2

Here you go, Amy. Good luck!

1.
Distribute the 5:

-(2a-15a+20)

Add the terms with the variable "a":

-(13a + 20)

Distribute the negative:
-13a +20


2.
Cross multiply across the = sign:
S(1-r)= a

Distribute the S:
S - Sr = a

Subtract S from both sides
-Sr = a-S

Divide by -S:
r = (a-S)/-S

3.
Distribute the -1 on the left and the 2 on the right:
8a - 2a + 8 = 8a -2

Add the terms on the left with the "a"s
6a + 8 = 8a -2

Subtract to get the "a" terms on one side and the numbers on the other:
10 = 2a

Divide by 2
5 = a

4.
Distribute the numbers outside the parenthesis:
3a-18-(4-8a)a = 8a^2

Distribute the a:
3a-18-4a+8a^2 = 8a^2

The 8a^2 terms cancel each other out:
-a -18 = 0

Solve for a:
a = -18

Answer 3

USE the mnemonic device, Please Excuse My Dear Aunt Sally. That is, Parenthesis, Exponents, Multiply, Divide, Add and finally Subtract.

1. Distribute the 5, giving you -15a +20. Or, -(2a -15a +20). Distribute the the -1, gives you -2a +15a -20. Final answer is +13a -20.

2. Remove denominator by multiplying both sides by (1-r) or
S(1-r) = a, Distributing S, then dividing by -S, you get
r = (a -S)/-S. Getting rid of the negative sign in the denominator ( by multiplying by -1 gives you r = (S-a)/S


3. 8a -2a +8 = 8a -2. Subtract, etc, should give you 10 = 2a or dividing by 2 gives a =5.

4. Again, distribute then combine like terms.
3a -18 -4(a-2a^2) = 8a^2. Note I multiplied (1-2a) by a first. If you have 3 factors being multiplied, do it stepwise to eliminate mistakes. Then distribute the -4.
3a -18 -4a +8a^2 = 8a^2. Combine like terms, etc and you get
-a = 18 or a = -18

Answer 4

1) This is basic distributive property... when you have something in the form of a(b + c) the result is a*b + a*c... so to simplify, you would do the following:

-[2a - (5)*(3a) - (-5)(4)] = -[2a - 15a + 20]

then the negative outside reverses the sign of everything, resulting in:

-2a + 15a - 20 = 13a - 20

2) you have S = a / (l-r) so you multiply both sides by (l-r) giving you:

S(l-r) = a

Now divide both sides by S to get:

l-r = a/S

now subtract l from both sides to get:

-r = a/S - l

now simply multiply both sides by -1 to get the answer:

r = l - a/S

3) Simplify the left side and distribute the right to get:

8a - 2a + 8 = 8a - 2 then simplify and combine:

6a + 8 = 8a - 2 now move all the a's to one side and constants to the other...

8a - 6a -2 = 6a - 6a + 8
2a - 2 + 2 = 8 + 2
2a = 10
a = 5

4) Distribute:

3a - 18 - 4a + 8a^2 = 8a^2

remove the 8a^2 from each side:

3a - 18 - 4a = 0

simplify:

-a - 18 = 0
a + 18 = 0
a = -18

Answer 5

#3 8a-(2a-b)=2(4a-1)
8a-(2a-8)=8a-2
8a-2a+10=8a
6a+10=8a
10=2a
a=5

Answer 6

i can't help but go to webmath.com