A quick method is to simply look at the graph and notice the two altitudes cross at (-1,0)
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A longer method involves a bit of algebra but its not too bad
y = x+1 y = -1+1 ... plug in x = -1 (ie replace x with -1) y = 0 So when x = -1, the value of y is y = 0 They pair up to get (x,y) = (-1,0) which confirms what the graph is showing
