Explanation for Question 3 From the Math (No Calc) Section on the 2020 March Sat
Now question number three says that the function F is defined by this quadratic 2 equation. And we want to know the value of F of four. 3 And so perhaps you missed this question because you don't really understand the notation 4 here. Right? We see here F of X and the F of 5 X is just a fancy way to say the Y value. 6 So when it says F of four, what they really want is a Y 7 value. And in order to have a Y value, 8 you have to know what X you're plugging in to begin with and notice 9 how the X is here in parentheses. Since there is a foreign parentheses here, 10 what we're really doing is finding the Y value when X 11 is equal to four, and if X is equal to four, 12 then I can just plug four into my equation and solve it from there. 13 Right? So F of four, 14 actually let's even go back. One more step F of X is equal to 15 X squared, minus five X plus six. 16 And I know that I want F of four. So now wherever there's an 17 X, I'm going to plug in a four instead. 18 So I have four squared minus five times four plus six. 19 We know that four squared is 16, five times four is 20, 20 the six remains a six, right? And so 2016 minus 20, 21 that's going to be negative four plus six, 22 right? That's negative, positive to positive two. 23 And so the answer that shows positive two is going to be B. 24 And so just to summarize, we can find our answer B by knowing that 25 we need to find the Y value when X is four, 26 and then they're plugging in four and getting our answer for the Y value.