Let f(x)=x(4-x)(x-6)f(x)=x(4−x)(x−6)
Let's do a sign chart
color(white)(aaaa)aaaaxxcolor(white)(aaaa)aaaa-oo−∞color(white)(aaaa)aaaa00color(white)(aaaaa)aaaaa44color(white)(aaaaaa)aaaaaa66color(white)(aaaaaa)aaaaaa+oo+∞
color(white)(aaaa)aaaaxxcolor(white)(aaaaaaa)aaaaaaa-−color(white)(aaaa)aaaa++color(white)(aaaa)aaaa++color(white)(aaaa)aaaa++
color(white)(aaaa)aaaa4-x4−xcolor(white)(aaaa)aaaa++color(white)(aaaa)aaaa++color(white)(aaaa)aaaa-−color(white)(aaaa)aaaa-−
color(white)(aaaa)aaaax-6x−6color(white)(aaaa)aaaa-−color(white)(aaaa)aaaa-−color(white)(aaaa)aaaa-−color(white)(aaaa)aaaa++
color(white)(aaaa)aaaaf(x)f(x)color(white)(aaaaa)aaaaa++color(white)(aaaa)aaaa-−color(white)(aaaa)aaaa++color(white)(aaaa)aaaa-−
For f(x)<=0f(x)≤0
The solution is x in [0,4] uu [6,+ oo[x∈[0,4]∪[6,+∞[
graph{x(4-x)(x-6) [-14.56, 13.9, -8.47, 5.77]}