Variable Substitution of a Function

2021 5 8
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更新时间：2021 5 9
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Hi everyone,
I have a simple question, but yet I can't figure it out. I want to substitute (point + alfa * d) values over x values.
If you evaluate (point + alpha * d), result is [1 - alpha, 2 - alpha]. But when it comes to the substitution, it becomes [alpha - 1, alpha - 2]. Why is that? How can I make this correct? Thanks in advance.
variable_count = 2;
syms x [1 variable_count]
syms alpha
func = 3 * x1^2 + 2 * x1 * x2 + 2 * x2^2 + 7;
d = [-1 -1];
point = [1 2];
func_one = subs(func, x, point + alpha * d)

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Paul
Paul 2021-5-8

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It is correct, isn't it?
x1^2 = (-x1)^2, x1*x2 = (-x1)*(-x2), and x2^2 = (-x2)^2

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Onur YURDAKUL
Onur YURDAKUL 2021-5-9
Yes, silly me. I was expecting just a raw substitution but instead it also rearranges the function. Thanks for your answer.

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