How do you solve (x-1)(x+2)(2x-5)<0(x1)(x+2)(2x5)<0 using a sign chart?

1 Answer
Jan 17, 2017

The answer is x in ] -oo,-2 [ uu ] 1, 5/2[ x],2[]1,52[

Explanation:

Let f(x)=(x-1)(x+2)(2x-5)f(x)=(x1)(x+2)(2x5)

Now, we can do our sign chart

color(white)(aaaa)aaaaxxcolor(white)(aaaaaa)aaaaaa-oocolor(white)(aaa)aaa-22color(white)(aaaa)aaaa11color(white)(aaaa)aaaa5/252color(white)(aaaaa)aaaaa+oo+

color(white)(aaaa)aaaax+2x+2color(white)(aaaaaa)aaaaaa-color(white)(aaaa)aaaa++color(white)(aaa)aaa++color(white)(aaaa)aaaa++

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

color(white)(aaaa)aaaa2x-52x5color(white)(aaaaa)aaaaa-color(white)(aaaa)aaaa-color(white)(aaa)aaa-color(white)(aaaa)aaaa++

color(white)(aaaa)aaaaf(x)f(x)color(white)(aaaaaaa)aaaaaaa-color(white)(aaaa)aaaa++color(white)(aaa)aaa-color(white)(aaaa)aaaa++

Therefore,

f(x)<0f(x)<0 when x in ] -oo,-2 [ uu ] 1, 5/2[ x],2[]1,52[