What's 21a + 28b factorise fully

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Identify the number as a rational or irrational.explain. 127

The description below represents function a and the table represents function b: function a the function is 5 more than 3 times x. function b x y −1 2 0 5 1 8 which statement is correct about the slope and y-intercept of the two functions? (1 point) their slopes are equal but y-intercepts are not equal. their slopes are not equal but y-intercepts are equal. both slopes and y intercepts are equal. neither slopes nor y-intercepts are equal.