Range dari f(x) = 3x² + 6x - 72 dengan daerah asal {x ? -8< x < 6, x ∈ R} adalah... Mohon Bantuannya

Himpunan daerah asalnya adalah {-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5}
f(x) = 3[tex] x^{2} [/tex]+6x-72 =(3x-12)(x+6)
f(-7) = (-33)*(-1) = 33
f(-6) = (-30)*(0) = 0
f(-5) = (-27)*(1) = -27
f(-4) = (-24)*(2) = -48
f(-3) = (-21)*(3) = -63
f(-2) = (-18)*(4) = -72
f(-1) = (-15)*(5) = -75
f(0) = (-12)*(6) = -72
f(1) = (-9)*(7) = -63
f(2) = (-6)*(8) = -48
f(3) = (-3)*(9) = -27
f(4) = (0)*(10) = 0
f(5) = (3)*(11) =33
Jadi Himpunan daerah hasil (range) adalah {-75,-72,-63,-48,-27,0,33,55}