compute a scalar r that is the sum of the first 2 elements plus the last 3 elements of x in matlab

You can compute a scalar r that is the sum of the first 2 elements plus the last 3 elements of x in MATLAB as follows:

main.m
x = [1 2 3 4 5]; % example input vector
r = sum(x(1:2)) + sum(x(end-2:end));
disp(r); % print the result
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This code snippet first defines an example input vector x. Then it computes r by taking the sum of the first two elements of x using the sum() function and the colon operator : to create a range of indices. It adds this to the sum of the last three elements of x, which is achieved by using the end keyword to reference the last index of x and subtracting 2 to get the third-to-last index, and combining this with the end keyword to create a range from the third-to-last index to the end of x.

The result is stored in the variable r and displayed using the disp() function. Note that you can substitute your own values or variable names for x as needed.