y = 2x - 5
Work out the value of y when x = -4
Answer (2)
To find the value of y when x = − 4 , substitute − 4 into the equation y = 2 x − 5 . After performing the calculations, you will find that y = − 13 .
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Substitute x = − 4 into the equation y = 2 x − 5 .
Calculate 2 × ( − 4 ) = − 8 .
Calculate − 8 − 5 = − 13 .
The value of y is − 13 .
Explanation
Understanding the Problem We are given the equation y = 2 x − 5 , and we need to find the value of y when x = − 4 . This is a straightforward substitution problem.
Substitution Substitute x = − 4 into the equation:
y = 2 ( − 4 ) − 5
Calculation Now, perform the calculation:
y = − 8 − 5
y = − 13
Final Answer Therefore, the value of y when x = − 4 is − 13 .
Examples
Imagine you are tracking the altitude of a drone. The altitude y (in meters) is related to the time x (in seconds) by the equation y = 2 x − 5 . If you want to know the altitude of the drone at x = − 4 seconds (which means 4 seconds before you started tracking), you can substitute x = − 4 into the equation to find the altitude. This kind of linear relationship is common in physics and engineering to model how quantities change over time or distance.
