The x- and y-intercepts are both 13, so the area is ...
... A = (1/2)bh = (1/2)·13·13 = 169/2 = 84.5 . . . square units
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Solve for x when y=0 to find the x-intercept:
... 0 = 13 - x
... x = 13 . . . . . add x
Solve for y when x=0 to find the y-intercept:
... y = 13 - 0
... y = 13 . . . . . additive identity property of 0
