#SAT practice Math problem got me stumped

29 messages · Page 1 of 1 (latest)

ornate isle
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So far I set z^9 = x, and rewrote it as 38x^2+bx+70, and then the factors would be (qx+r)(sx+t), so I also set up a system where qs = 38, qt+rs = b, and rt = 70. Then if you rearrange the first and third in the system as s = 38/q and t = 70/r you can plug in and get the middle one to be: b = 70(q/r) + 38(r/q). This is where I'm stuck. What do I do from here, if I've gone down the right path, or am I completely lost and is there a different, correct way to do it?

surreal kiteBOT
slim heath
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this is the eqation you have obtained

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b = 70(q/r) + 38(r/q)

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since (qx+r) is a factor, it satisfies the equation 38x^2+bx+70

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hence x = -r/q will be a root. input that in the equation 38x^2+bx+70

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you will obtain an eqn like 38t^2 - bt +70 = 0, where t = -r/q

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obtain value of t by quadratic formula

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put that in b = 70(q/r) + 38(r/q)

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let me know if that worked

ornate isle
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And also thanks for helping out on this

slim heath
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oh well you can just go ahead with x = -r/q

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my OCD ass is dead intent on making things look neat and oversimplified

ornate isle
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Ohh instead of x you put t

slim heath
ornate isle
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I was a little confused because t was in one of my roots

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Okay thanks let me do that real quick

surreal kiteBOT
ornate isle
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Would b = 5320?

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Wait hold on

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Nevermind that's just the b^2 of the quadratic formula part lemme do the whole thing

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So then just sqrt(5320)?

slim heath
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can you show me the work?

slim heath
ornate isle
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I literally just lost sight of my work and was trying to find where I was for like the past 15 minutes

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Theres so many variables to keep track of

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Here's what I put if any of it makes sense, let me know what you did after step where x = -r/q