Question 1031346
Right rectangles 

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ONE GOOD ADVICE:  Learn how to write the symbols relevant to your questions if you want to be taken seriously. 

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The width of each rectangle would be {{{(b-a)/n}}}, while the height of the rectangle would be given by {{{f(x[k]) = y[k]}}}, where {{{1 <= k <= n}}}, which corresponds to the right endpoint of a sub-interval. The approximation would be

{{{(b-a)/n}}}({{{y[1]+y[2]+y[3]}}}+...+{{{y[n-1]+ y[n]}}}).