Question

Помогите с алгеброй
Д, б, г

Answer 1

д)

$left { {{x^2+5x<0} atop {x>-7}} right. \ \ left { {{x(x+5)<0} atop {x>-7}} right. \ \ left { {{xin(-5;0)} atop {xin(-7;+oo)}} right. \ \otvet: xin(-5;0)$

б)

$left { {{21x^2+39x-6<0} atop {x>0}} right. \ \ D=39^2+4*21*6=1521+504=2025=45^2\ \ x_{1}= (-39-45)/42=-2\ \ x_{2}= (-39+45)/42=1/7\ \ left { {{xin(-2;1/7)} atop {xin(0;+oo)}} right. \ \ otvet:xin(0;1/7)$

г)

$left { {{x^2-144>0} atop {x-3<0}} right. \ \ left { {{(x-12)(x+12)>0} atop {x<3}} right. \ \ left { {{xin(-oo;-12)U(12;+oo)} atop {xin(-oo;3)}} right. \ \ otvet:{xin(-oo;-12)$