If a + b =5 and a-b = 3 then the value of a² + b² should be

17

if A+B= 5 and a-b=3, then a=4 and b=1. So, 4^(2)+1^(2)= 16+1=17

No, the triangular numbers are not a direct variation. There is not a constant of variation between a number and its position in the sequence. The ratios of the numbers to their positions are not equal. Also, the points (1, 1), (2, 3), (3, 6), and so on, do not lie on a line.

Hope this helps!!! :)