快速and穩陣搞掂function魔王題！

[@tobysoft2346]

你係UA-cam 講得最清晰嘅數學Channel ! Thank you so much ❤ 請問type4係類似U-substitution？

[@乔反]

講得好清楚！！！！超期待你接下來的片！！！！

[@mr.m-train0608]

最尾嗰條將x代35x-13

[@hongningsuen1348]

Type 1 problem of subtitution into function - given f(x) = polynomial of x
Example: f(x) = x^2 + 3x + 5
Subtitution of number into f(x) gets a number.
f(-2) = (-2)^2 +3(-2) + 5 = 3
Substitution of polynomial into f(x) gets a polynomial.
f(2x +1) = (2x + 1)^2 + 3(2x + 1) + 5 = 4x2 + 10x + 9
Type 2 problem of substitution into function - given f(polynomial of x) = polynomial of x
Example: f((x + 3)/5) = x^2 + 3x + 5
Tranform to type 1 problem by changing f(polynomail) to f(variable):
Let (x + 3)/5 be y. (x + 3)/5 = y => x = (5y - 3)
f(y) = x2 + 3x + 5 = (5y - 3)^2 + 3(5y - 3) + 5 = 25y^2 - 15y + 5
f(1) = 25(1)^2 - 15(1) + 5 = 15
f(x) = 25x^2 - 15x + 5
f(7x - 2) = 25(7x - 2)^2 - 15(7x -2) + 5 = 1225x^2 - 805x + 135

[@sygd925]

仲吾貼吓2024嘅嘢！😣