Please no one else butt in because I actually want to help RB to understand.
Hi RB,
I like the way tyou said that.
I often say, I understand ... but ... I don't really understand.
There are different levels of understanding in mathematics.
Let's see if I can help.
I'll do the first one and then you can try the others.
1) \(f(x)=2x-5\qquad find\;\;\quad f(6) \quad and \quad f(1)\)
For f(6) you are replacing all the x'es with 6
so
\(f(6) = 2*6 - 5 = 12-5 = 7\)
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For f(1) you are replacing all the x'es with 1
so
\(f(6) = 2*1 - 5 = 2-5 = -3\)
NOW you have a go at at least one of the other questions. show me your working, and I will see if I can help you get to the point of REALLY understanding