(x²+5x+4)(x²+5x+6)=120 let x²+5x=y solve
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(x²+5x+4)(x²+5x+6)= 120
(y+4)(y+6)= 120
y²+6x+4x+24= 120
y²+10x+-96=0
y²+16y-6y-96=0
y(y+16)-6(y+16)=0
(y-6)(y+16)=0
y-6=0 / y+16=0
y=6 / y=-16
x²+5x= 6
x²+5x-6=0
x²+3x+2x-6=0
x(x+3)+2(x+3)=0
x+2=0 / x+3=0
x=-2 / x=-3
(y+4)(y+6)= 120
y²+6x+4x+24= 120
y²+10x+-96=0
y²+16y-6y-96=0
y(y+16)-6(y+16)=0
(y-6)(y+16)=0
y-6=0 / y+16=0
y=6 / y=-16
x²+5x= 6
x²+5x-6=0
x²+3x+2x-6=0
x(x+3)+2(x+3)=0
x+2=0 / x+3=0
x=-2 / x=-3
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