Explanation for Question 30 From the Math (Calc) Section on the 2020 March Sat
So looking at question 30, it tells us that the expressions X squared plus 2 BX, plus 10 and X minus three squared plus C or B and C 3 are constants. So when it says BNC or Constance, 4 it just means that they're normal numbers and B will always be the same 5 number. And C will always be the same number are equivalent. 6 So basically this expression is the same thing as this expression. 7 And it wants to know what is the value of B plus C? 8 Right? So what I'm really going to do here is since I know that 9 these are equivalent a good start, we'll be writing an equation where I've set 10 them equal to each other. 11 So that X squared plus BX plus 10 is equal to, 12 or equivalent to X minus three squared plus C. 13 Alright, and I need to know what the value of B plus C is. 14 So now what I'm going to do is I'm 15 going to zoom in on here and we can see that perhaps C is 16 equal to 10, 17 right? Perhaps we want to get C into a way where it's close to 18 being equal to 10, because C is a normal number and here's a normal 19 number, but now I have this. 20 So if I want these two to look more similar, 21 right? So that I can think about what B might be and what C 22 might be. Then what I should do is foil this out, 23 right? So we've got X minus three times X minus three. 24 And if I foil that out, I'll get X squared, 25 minus three X minus three X, 26 and then plus nine, right? So let's rewrite this out. 27 We have X squared plus BX. 28 Plus 10 is equal to X squared, 29 minus six...