height times base equals area ... h • b = A
x • (x + 9) = 112
multiply it out x2 + 9x = 112
subtract 112 from both sides x2 + 9x – 112 = 0
factor the quadratic (x + 16)(x – 7) = 0
set each factor equal to zero x + 16 = 0 so x = –16 discard, because a side can't be negative
at least not in three-dimensional space
x – 7 = 0 so x = 7 this is the height
base equals 9 more than height 7 + 9 = 16 this is the base
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