How do you solve (x-1)(3x-4)>=0(x1)(3x4)0 using a sign chart?

1 Answer
Dec 6, 2016

The answer is x in ] -oo,1 ] uu [ 4/3, +oo[ x],1][43,+[

Explanation:

Let f(x)=(x-1)(3x-4)f(x)=(x1)(3x4)

Let's do the sign chart

color(white)(aaaa)aaaaxxcolor(white)(aaaa)aaaa-oocolor(white)(aaaa)aaaa11color(white)(aaaa)aaaa4/343color(white)(aaaa)aaaa+oo+

color(white)(aaaa)aaaax-1x1color(white)(aaaa)aaaa-color(white)(aaaa)aaaa++color(white)(aaaa)aaaa++

color(white)(aaaa)aaaa3x-43x4color(white)(aaaa)aaaa-color(white)(aaa)aaa-color(white)(aaaa)aaaa++

color(white)(aaaa)aaaaf(x)f(x)color(white)(aaaaaa)aaaaaa++color(white)(aaaa)aaaa-color(white)(aaaa)aaaa++

So, f(x)>=0f(x)0 for x in ] -oo,1 ] uu [ 4/3, +oo[ x],1][43,+[

graph{y=(x-1)(3x-4) [-1.863, 3.006, -1.232, 1.2]}