Respuesta :

answer is c) 24
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x^2 + 2(x)(12) + 12^2 
= x^2 + 24x + 144
= (x+12)^2
x^2+cx+144
it is like a^2+2a*b+b^2=(a+b)^2

here a=x ,b=12 and 2a.b=cx c=2*x*12=cx
c=24