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Every week I add 2-3 new video to collection ✔SUBSCRIBE and hit the 🔔 icon to get new video 1st video nov 2022
This is at least 2 times longer than it needs to be maybe even 3 times. You could have rearranged 1 and subbed directly into 2 and solved the resulting quadratic from there.
You receive a thumbs down for the "misleading title". Thus is a math problem for grade 8, and your solution is very well detailed, I'd say detailed enough such that any average 7th grade student understands what you did. A suitable title for your post is "Can you solve this 8th-grade math question in a way that a 7th grade understands what you did?"👎👎👎
I gave a thumbs down, not for the content (which I didn't even view), but for the misleading title containing "math olympiad". Anyone who have already learned Vieta's formulas in the school (8th grade) knows how to solve this.
Why take such a circuitous route, deriving xy=-15, and then refactoring to (x+3)(x-5)=0? Wouldn't it be more straightforward to just substitute y=2-x into the second equation giving x^2 + (2-x)^2 = 34 which simplifies directly to x^2 - 2x -15 = 0 and then use the roots of a quadratic equation formula from there?
If you simply expand the fraction with three you get this answer at once! But there is still a third root, so is that really simpler? Or is this once again 6:36 min of bullshit?
7*8*9*10!=7! 7 cannot be breaked and and according to the the problem, 7*8*9*10 is possible to be expressed in factorial.Hence the 7*8*9*10 will end as follows 1*2*3*4*5*7. No calculation required and speedy mental math here can adduce the answer. Comment please
Don't understand what the first three minutes of the video is for with all those extra useless steps since it is obvious that x! equals 7 * 8 * 9 * 10. That would have been my starting point. Showing that this equals 7! is very clever however.
Very easy. For everyone who knows complex numbers. This kind of equation is taught in high school. And you lost a lot of time making division. When you counted discriminant b^2-4ac = (-6)^2-4*1*36 we can notice it's 36 - 4*36 so we can take out 36 outside the bracket: 36 * (1 - 4) = 36*(-3). Square root is immediately 6*sqrt(3) i
y = 6-x so xy = x(6-x). Therefore x(6-x) = 36. That gives x^2 - 6x + 36 = 0, Solve using the quadratic fromula: x = ( 6 ± √(36 - 4*36) ) / 2 = ( 6 ± √( - 3*36) ) / 2 = ( 6 ± 6i√3 ) / 2 = 3 ± 3i√3. Since the equations are symmetrical in x and y, these must be the conjugate solutions for y, hence y = 3 ∓ 3i√3. That is mainly mental arithmetic and doesn't take 9 minutes. Was it the Toytown Math Olympiad?
Oups ! I just compute that both (½(-1-i√3))³=1 and (½(-1+i√3))³=1. So these two complex values are not solution of the x³-8=0 equation ! I expected that the three solutions of the equation x³-8=0 are { 2 ; -1+i√3 ; -1-i√3}. You may have made a mistake at the very end of your very long long algebraic fairway. Try to be more efficient in algebraic expression manipulations. You may understand that only teachers are decomposing so much each step: it is just for educational purposes. The mathematician's practices lead them to a more concise and efficient notation's handling. And don't forget to always check your results