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# Find the requested value.

f(-5) for f(x) = {7x     if x ≤ -1
{x-9    if x > -1

### 2 Answers by Expert Tutors

Shelly J. | Excellent Maths Tutoring for academic successExcellent Maths Tutoring for academic su...
5.0 5.0 (248 lesson ratings) (248)
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Hi Jay,

we have to find the value for f(-5)

The equation f(x)=7x gives the value of f(x) when x is less than or equal to -1.

The equation f(x)=x-9 gives the value of f(x) when x is greater than -1.

since -5 is less than -1

so we will take the equation f(x)=7x to find the value for f(-5)

f(-5)=7(-5)=-35
David T. | Experienced Math and Physics TutorExperienced Math and Physics Tutor
4.8 4.8 (12 lesson ratings) (12)
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In this example we will be substituting the value (-5) for x in the expression given.

The critical question is:

is -5 more or less than -1?

If it is less, then you use the first expression:  f(x) = 7x.

If it is more, then you use the second expression:  f(x) = x-9.

The actual numerical evaluation will proceed exactly as you would expect after that point.