PDA

View Full Version : Factoring



04-20-2006, 04:56 PM
In factoring a complete equation what am I doing wrong on my test i messed 8 and it made me flunk the test. These are a example of some probelms:

1. 3a^2-21a+18

first you would find the common demonantor whcih would be 3 the answer that i got was 3(a-6)(a-1) is this correct?

2. 9x^2 =25x-6

the answer that I got was (9x-2)(x+3)?

3. 4a^2b^3+ab^4-4ab^4-b^5

the answer that i got is (4ab^3=b^4)(a-b) is this right?

4. b^2-7b-44

the answer is (b+22)(b-2)?

5. 45a^3d-75a^2d^2-30ad^3

the answer that I got is 15ad(3a+d)(a-2d) is this right?

6. 3x^2-x-10

the answer is (3x-5)(x=2) is this right?

7. 2x^2-10x-28

the answer will be 2(x-2)(x+7) is this right?

Thanks for all your help I really apprecaite it alot. Maybe I can use this site for my family

skeeter
04-20-2006, 06:09 PM
In factoring a complete equation what am I doing wrong on my test i messed 8 and it made me flunk the test. These are a example of some probelms:
1. 3a^2-21a+18 first you would find the common demonantor I think you mean "common factor" whcih would be 3 the answer that i got was 3(a-6)(a-1) is this correct? yes

2. 9x^2 =25x-6 the answer that I got was (9x-2)(x+3)?
is this the equation 9x^2 = 25x - 6 or the expression 9x^2 + 25x - 6?

3. 4a^2b^3+ab^4-4ab^4-b^5 the answer that i got is (4ab^3=b^4)(a-b) is this right?
yes, if that = sign typo is supposed to be a +

4. b^2-7b-44 the answer is (b+22)(b-2)?
nope ... (b - 11)(b + 4)

5. 45a^3d-75a^2d^2-30ad^3 the answer that I got is 15ad(3a+d)(a-2d) is this right?
yes

6. 3x^2-x-10 the answer is (3x-5)(x=2) is this right?
yes ... if the typo = sign is really a +

7. 2x^2-10x-28 the answer will be 2(x-2)(x+7) is this right?
close ... 2(x+2)(x-7)

stapel
04-20-2006, 06:15 PM
1) There are no fractions here, so why would you be trying to do something with (non-existant) denominators? Please clarify. Thank you.

2) What is the "equals" supposed to be?

3) What is the "equals" in your answer supposed to be?

4) Factoring can be checked by multiplying:

. . . . .(b + 22)(b - 2) = b<sup>2</sup> + 22b - 2b - 44 = b<sup>2</sup> + 20b - 44

Is this what you'd started with?

5) Your answer is correct.

6) What is the "equals" in the answer meant to be?

7) Check:

. . . . .2(x - 2)(x + 7) = 2[x<sup>2</sup> - 2x + 7x - 14] = 2x<sup>2</sup> + 10x - 28

Is this what you started with?

Eliz.