The approach to take depends on the marking scheme : quickest method or method expected to demonstrate algebraic skills. The approach shown is an excellent demonstration of algebraic skill : if the marking scheme is based on this, it is the way to go. If speed is the only criteria, with this problem structure, reconstructing the question is the fastest method. 1. RHS is integer. LHS is integer : assume perfect cubes for the values cube rooted. 2. The difference of the cube roots is 2. 3. The difference of the cubes is 98. (The difference of +49 and -49). Investigating perfect cubes 1 1 2 8 3 27 4 64 5 125 Applying criteria 2. and 3., the cubes are 125 for 1st LHS term and 27 for 2nd. For the 1st term, 125 = 4x + 49, x = 19. For the 2nd term, 27 = 4x - 49, x = 19. CONCLUSION X = 19
Why didn’t you solve equation 1&3 simultaneously. I know you need to make the video longer but student are on the clock during exam. There is no time to rigmarole
GENERAL COMMENTS on your video I observed that you spend time on useless calculations for quadratic equations. 1. in case of a-b = m, ab = n , You solve it by finding a + b with (a+b)^2 = (a-b)^2 + 4ab instead of using a(a-m) = n 2. in case of a+b = m, ab = n You solve it by finding a-b with (a-b)^2 = (a+b)^2 - 4ab instead of using Vieta's formula.
Nice solution
I'm glad you found it helpful 🙏💕😎💯
@superacademy247 ❤
49 not 's equal to 76
The approach to take depends on the marking scheme : quickest method or method expected to demonstrate algebraic skills.
The approach shown is an excellent demonstration of algebraic skill : if the marking scheme is based on this, it is the way to go.
If speed is the only criteria, with this problem structure, reconstructing the question is the fastest method.
1. RHS is integer. LHS is integer : assume perfect cubes for the values cube rooted.
2. The difference of the cube roots is 2.
3. The difference of the cubes is 98. (The difference of +49 and -49).
Investigating perfect cubes
1 1
2 8
3 27
4 64
5 125
Applying criteria 2. and 3., the cubes are 125 for 1st LHS term and 27 for 2nd.
For the 1st term, 125 = 4x + 49, x = 19.
For the 2nd term, 27 = 4x - 49, x = 19.
CONCLUSION
X = 19
let a = (4x + 49)^1/3, b = (49 - 4x)^1/3 => a + b = 2 , a^3 + b^3 = 98
=> a^3 + b^3 = (a + b)^3 - 3ab(a + b) = 8 - 6ab = 98 => ab = -15
=> from a + b = 2, ab = -15 , a,b are roots t^2 - 2t -15 = (t + 3)(t - 5) = 0
=> a = {-3, 5} => x = {-19, 19}
a-b=2; a^3-b^3=98;
>(a-b)^3=a^3-b^3+3ab(a-b)=>2^3=98+3ab(2)=> 8-98=6ab=-90; =>ab=-15 ;(b=a-2);=>a^2-2a+15=0;=> (a-5)(a+3)=0;=> a=5 or-3;
&b=3 or -5; =>=> x=±19
Thanks for sharing your insightful calculation💖💯🙏😎
@@superacademy247 like you being appreciative, you are super academy 👍🙏
Thanks a lot 💯🤩✅🙏
Why didn’t you solve equation 1&3 simultaneously. I know you need to make the video longer but student are on the clock during exam. There is no time to rigmarole
Totally agreed. I wrote the same thing in the comments.
левой пяткой почесать правое ухо можно. но зачем?🙈
GENERAL COMMENTS on your video
I observed that you spend time on useless calculations for quadratic equations.
1. in case of a-b = m, ab = n ,
You solve it by finding a + b with (a+b)^2 = (a-b)^2 + 4ab instead of using a(a-m) = n
2. in case of a+b = m, ab = n
You solve it by finding a-b with (a-b)^2 = (a+b)^2 - 4ab instead of using Vieta's formula.
Thanks for your valuable feedback. I'll keep that in mind for future videos!
Thanks for your valuable feedback. I'll keep that in mind for future videos! Thanks for sharing your in-depth perspective! 💯💪