Answer: 378
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Work Shown:
f(x) = x^2 - 3x
f(x) = ( x )^2 - 3*( x )
f(-18) = ( -18 )^2 - 3*( -18 ) ... replace every x with -18; now use PEMDAS
f(-18) = 324 - 3*( -18 )
f(-18) = 324 + 54
f(-18) = 378
