maths help

[alexxxxx]

if f(x)=4x-3 and g(x)=2-x, what does gf(x)=?

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[DieselShaq]

f(x) = 4x-3
g(x) = 2-x

gf(x) basically means you do f(x) first and then use f(x) as x for g(x). Putting this in simpler words, f(x) is the x in g(x).
In this case, 4x-3 is x, which means that gf(x) = 2-(4x-3) or 2-4x+3, which is 5-4x.

I don't know if the above is clear enough, but here's a mathematical way:
gf(x) = ?
Let f(x) be (y)
gf(x) = g(y)

Here's another example:
f(x) = 3x+2
g(x) = 2x+1
gf(x) = ?

Substitute 3x+2 as x in g(x). g(x) therefore equals 2(3x+2)+1 = 6x+4+1 = 6x+5.

[alexxxxx]

thankyou so much +REP