Function substitution method problem! Do not understand: F (x + 1) = x & # 178; + 3 find f (x) substitution, use t = x + 1, and finally write t back to x, then Why can't we replace x + 1 with X first?

Of course not
f（x+1）=x²+3
You can make it by matching
f（x+1）=x²+3=（x+1)^2-2*(x+1)+4
Then you replace each x + 1 as a whole with X
We get f (x) = x ^ 2-2 * x + 4
The so-called substitution is to take a formula as a whole and replace it with a variable
If you want to change, you have to take x + 1 as a whole

The function f (x + 2) = 2x + 4, the analytic expression of F (x) is obtained by the method of substitution

Let x + 2 = t, then f (T) = 2T, f (x) = 2x

To find the analytic formula F (x + 1) = x * + 2x by substitution, if x = 2, is 2 brought into the analytic formula or 2 + 1 brought into the analytic formula

Substitution means to find f (x) by substitution
Let t = x + 1, x = T-1
f(t)=(t-1)²+2(t-1)=t²-1
f(x)=x²-1
f(2)=2²-1=3

Finding the analytic formula of function f = 2x + √ 1-3x by substitution method

Let √ (1-3x) = t, then x = (1-T & sup2;) / 3, t ≥ 0
∴y=[2(1-t²)/3]+t=-(2t²-3t-2)/3
This is the analytical formula

Function substitution method problem! Do not understand: F (x + 1) = x & # 178; + 3 find f (x) substitution, use t = x + 1, and finally write t back to x, then Why can't we replace x + 1 with X first?