For this type of question, we identify the signage of the coefficient of x2, whether it is positive or negative. We must also factorise to find the critical values of x which make the expression 0. In the first case, (4x - 5) (3x + 1) = 0 gives x = 5/4, x = -1/3, so these are the critical values.

If the coefficient of x2 is positive, then you will obtain a smiley face graph or a '+ - +'. In other words, the graph will be positive before the lower critical value, negative in between the critical values and positive after the higher critical value.

Similarly, if the coefficient of x2 is negative, then you will obtain a sad face graph or a '- + -'. In other words, the graph will be negative before the lower critical value, positive in between the critical values and negative after the higher critical value.

In the case of the first question, the lower critical value is -1/3 and the higher critical value is 5/4. Because this is a smiley face graph, we get a '+ - +', or in other words, positive value of the expression (4x - 5) (3x + 1) when x < -1/3 or x > 5/4, and negative value when -1/3 < x < 5/4.