Cubic Formula Proof Step 5: Putting it All Together to Solve for x
In this video I go over the fifth and final step of the Cubic Formula proof which involves putting all of the previous steps together to solve for the 3 solutions of x. The first solution of x is obtained by plugging in the first solution of y into the x-y substitution and replacing the p, q values with the a, b, c values. The second solution is obtained by simply copying the first solution and multiplying it by the corresponding complex conjugates from the cube root of unity. The third and final solution is obtained by copying the second solution and simply changing the signs of the complex conjugates. Because I used the copy and paste method in Microsoft OneNote, I may be the first person to show the complete solution being derived in real-time!
Timestamps
- Step 5: Plugging the y values into the x equation and replacing the p, q values: 0:00
- First solution for x: 2:20
- Second solution for x by copying the first solution and multiplying by complex conjugates: 8:20
- Third solution by copying the second solution and changing the signs of the complex conjugates: 11:32
- Double checking our solutions with the @blackpenredpen solutions: 12:03
Notes and playlists
- Playlist: https://www.youtube.com/playlist?list=PLai3U8-WIK0EF05ExjzLbB64NgUjoV1hl
- Notes: https://peakd.com/hive-128780/@mes/dzekfnxh .
Become a MES Super Fan! https://www.youtube.com/channel/UCUUBq1GPBvvGNz7dpgO14Ow/join
DONATE! ʕ •ᴥ•ʔ https://mes.fm/donate
SUBSCRIBE via EMAIL: https://mes.fm/subscribe
MES Links: https://mes.fm/links
MES Truth: https://mes.fm/truth
Official Website: https://MES.fm
Hive: https://peakd.com/@mes
Email me: [email protected]
Free Calculators: https://mes.fm/calculators
BMI Calculator: https://bmicalculator.mes.fm
Grade Calculator: https://gradecalculator.mes.fm
Mortgage Calculator: https://mortgagecalculator.mes.fm
Percentage Calculator: https://percentagecalculator.mes.fm
Free Online Tools: https://mes.fm/tools
iPhone and Android Apps: https://mes.fm/mobile-apps
▶️ 3Speak
!summarize
Part 1/5:
Understanding the Solution of Cubic Equations
Cubic equations can present a complex challenge, yet they follow a systematic approach for their solution. This article dives into the step-by-step process to find the roots of a cubic equation of the form ( ax^3 + bx^2 + cx + d = 0 ).
Step Five: Assembling the Components
The solution to a cubic equation involves determining the values for ( x_1 ), ( x_2 ), and ( x_3 ) using the previously computed values ( y_1 ), ( y_2 ), and ( y_3 ). The primary goal is to transition from terms ( p ) and ( q ) back to the original coefficients of the cubic equation ( a ), ( b ), ( c ), and ( d ).
Correcting Errors
Part 2/5:
Throughout the process, maintaining accuracy is crucial. Reflecting back, it's important to note a minor error discovered in a previous calculation where an incorrect term was added. Initially, a three was mistakenly placed where a two should have appeared: ( -\frac{b^2}{3a} ) was mistakenly modified. Clarifying and correcting these calculations is essential for achieving the right outcomes.
Finding Values of ( p ) and ( q )
As the next phase begins, we revert to previously derived values of ( p ) and ( q ), essential for our computations moving forward. The substitution principle involves transforming ( x = y + K ), where ( K ) is defined as ( \frac{b}{3a} ). This conversion allows us to compute ( x ) values by substituting ( y ) values combined with ( K ).
Part 3/5:
Solving for ( x_1 ), ( x_2 ), and ( x_3 )
Using the first calculated term ( y_1 ), we derive ( x_1 ) with the formula ( x_1 = y_1 - \frac{b}{3a} ). The process continues by systematically substituting computed values of ( y_1 ) and examining the equations step-by-step.
To illustrate, if ( y_1 = \frac{3Q}{2} + ... ), we adjust this by incorporating ( K ) to establish the precise value of ( x ).
Constructing Other Roots
After determining ( x_1 ), the procedure for finding ( x_2 ) and ( x_3 ) parallels that of ( x_1 ). It involves recognizing conjugate terms from the polynomial like ( W_1 ) and ( W_2 ). Here, careful attention is needed as signs toggle between the roots.
Summarizing the Results
Part 4/5:
At the conclusion of these calculations, each ( x ) value should replicate the format of the cubic equation solution. This systematic arrangement aids in confirming our final expressions for ( x_1 ), ( x_2 ), and ( x_3 ).
Final Check: Validating the Solutions
Before concluding, it is prudent to double-check the entirety of our solutions to ensure accuracy. Reviewing samples reflected in authoritative mathematical resources or demonstrations, such as a popular YouTube channel highlighting cubic solutions, allows for a comprehensive comparison and verification of results.
Conclusion: The Essence of Solving Cubic Equations
Part 5/5:
The path to finding ( x_1, x_2, ) and ( x_3 ) from the cubic equation is intricate yet manageable with diligence. This approach emphasizes the importance of systematic corrections and methodical substitutions in producing reliable solutions, showcasing the beauty and complexity of algebraic processes. As these calculations unfold, they reveal the powerful connections within polynomial equations and their respective roots, enriching our overall understanding of mathematics.