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Mathematics 9 Online
OpenStudy (anonymous):

HELP ME PLEASE, PICTURE ATTACHED WILL GIVE MEDAL AND FAN

OpenStudy (anonymous):

OpenStudy (anonymous):

@e.mccormick @mathstudent55 @precious32 @zepdrix @Zioh @zzr0ck3r @Luigi0210 @MonaLove

OpenStudy (anonymous):

@Whitemonsterbunny17 @asatt32 @Eytan99 @Wolfboy @RosieF

OpenStudy (mathstudent55):

Let's look at where the trinomial comes from. Instead of starting with a trinomial that needs to be factored, and then you don't know for sure if the trinomial can be factored until we try, we will start with a product of two binomials. What is (2x + 3)(3x - 4) = ? Can you use FOIL and find the trinomial?

OpenStudy (anonymous):

yes

OpenStudy (mathstudent55):

What do you get?

OpenStudy (anonymous):

wait i'm going to do it now

OpenStudy (mathstudent55):

ok

OpenStudy (anonymous):

\[6x^2+x-12\] uhm im not quit sure if its that

OpenStudy (mathstudent55):

Yes, you're correct.

OpenStudy (mathstudent55):

Ok. Now we have a trinomial of the form ax^2 + bx + c that definitely can be factored because we got it by multiplying two binomials together.

OpenStudy (mathstudent55):

The way I factor these trinomials is using the ac method. This method is used to factor a trinomial of the form \(ax^2 + bx + c\) The ac method: 1. Multiply ac together. 2. Find two factors of ac that add up to b. Call them p and q. 3. Break up bx into two parts, px and qx. 4. Factor the by grouping.

OpenStudy (mathstudent55):

Now let's look at our trinomial. \(6x^2 + x - 12\) 1. Multiply ac: \(6 \times (-12) = -72\) 2. Find two factors of ac that add up to b. ac = -72; b = 1 \(9 \times (-8) = -72\) \(9 + (-8) = 1\) 3. Break up the term bx using the two factors we found above. \(6x^2 + 9x - 8x - 72 \)

OpenStudy (mathstudent55):

I just noticed that with our trinomial, a and b are positive, and c is negative. Your problem states that a is positive and b and c are negative. Let's modify our trinomial a little. Let's start with this product. (2x - 3)(3x + 4) We use FOIL to get: \(6x^2 -x - 12\) Now we have a = 6, positive, and b = -1, negative, and c = -12, also negative just like the problem states.

OpenStudy (mathstudent55):

Now let's do the ac method again for factoring. 1. Multiply ac: 6×(−12)=−72 2. Find two factors of ac that add up to b. ac = -72; b = 1 \(-9 \times = −72\) \(-9 + 8 =-1\) 3. Break up the term bx using the two factors we found above. \(6x^2 -9x+8x−72 \)

OpenStudy (mathstudent55):

Ok. Now let's look at your question.

OpenStudy (mathstudent55):

\(\large6x^2 - x - 12 = 6x^2 - 9x + 8x - 72\) a is positive, and c is negative, so ac is negative. The two factors we find, that the problem calls m and n, must be one positive and one negative, so that their product can be negative.

OpenStudy (mathstudent55):

We can call m = -9 and n = 8, or m = 8 and n = -9, so we don't know which one is larger than the other. All we know is that one is positive and one is negative.

OpenStudy (anonymous):

is it B

OpenStudy (anonymous):

i think it is

OpenStudy (mathstudent55):

B has both numbers negative. I think one number needs to be positive and the other one negative. I don't understand the part about |m| > |n| and |n| > |m|.

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