If f(x)=7-4x, given that f(c)=9, find c
f(c) means let x=c. Remember that c is just an unknown number.
The expression f(c)=9 means that when we put c through the function f(x)=7-4x, it gives the answer 9. Therefore we know 7-4c=9 is true.
Now we have an equation that we can go through in the normal way:
7-4c=9
-4c=2
4c=-2
c=-0.5
EF
Related Maths GCSE answers
All answers ▸Expand (2x-4)(x+3)
ABC, DEF and PQRS are parallel lines. BEQ is a straight line. Angle ABE = 60° Angle QER = 80° Work out the size of the angle marked x. Give reasons for each stage of your working.
Factorise fully 6x^2-14x
I find the percentage questions really hard, how do I answer the questions that will come up in exams?