651 views

### 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

2 years ago

Answered by Emma, a GCSE Maths tutor with MyTutor

## Still stuck? Get one-to-one help from a personally interviewed subject specialist

#### 787 SUBJECT SPECIALISTS

£22 /hr

Degree: Biochemistry (Bachelors) - Bristol University

Subjects offered:Maths, Chemistry+ 1 more

Maths
Chemistry
Biology

“ABOUT ME: I am a biochemistry student, currently studying at the University of Bristol, and have had a passion for the natural sciences from a very young age. I am patient, hardworking and experienced, having tutored students in Maths...”

£20 /hr

Degree: Medicine (Bachelors) - University College London University

Subjects offered:Maths, Chemistry+ 2 more

Maths
Chemistry
Biology
-Medical School Preparation-

“Hello I'm Samuel Aston and I'm a second year UCL medic looking for students needing help in attaining their full potential and the top marks!”

£18 /hr

Degree: Chemical Engineering MEng (Integrated Masters) - Newcastle University

Subjects offered:Maths, Chemistry

Maths
Chemistry

“I love maths, chemistry and biology and my passion for these subjects is something that will help teach students.”

MyTutor guarantee

Currently unavailable: for regular students

Degree: Medicine (Bachelors) - St. Andrews University

Subjects offered:Maths, -Personal Statements-+ 1 more

Maths
-Personal Statements-
-Medical School Preparation-

“Hi there! My name is Emma and I am currently a 2nd year medical student at the University of St. Andrews. GCSE Mathematics: Maths was always one of the subjects I enjoyed most at school - when faced with a problem that initially ...”

MyTutor guarantee

### You may also like...

#### Other GCSE Maths questions

When will I use any maths in real life?

What is the largest possible length of a pole you could fit in a room?

How would you solve the equation X^2+3x=10

Solve 3x - 5 < 16

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this.