本质教育论坛

Maths inequality

For question 74 in math book inequality, I did figure out

12x^2-31x+20> 0 and later = (3x-4)(4x-5)

also understood x= 4/3 oe 5/4

BUT I didn’t get in this case but didn’t get why would X be> 4/3 or < 5/4 and cannot be in between?

One more question on Q78 I understand (X-1) (X-3) (X+2)(X+4)>0

hence X>1,3,-2, -4

But do we plug in the number to solve the equation or is there a quicker way?

It is explained well in the book. Draw the number line and discuss.

Dear Serena, there is a quicker way to solve this kind of questions. I will explain to you in person later.