Explanation for Question 19 From the Math (No Calc) Section on the Official Sat Practice Test 7
Question 19 says the graph of a line in the X, 2 Y plane passes through the 0.1, 3 four and crosses the x-axis at the point to zero, 4 the line crosses the Y axis at the 0.0 B what is the value 5 of B? So to solve this problem, 6 we're going to need to use the Y equals MX plus B formula, 7 which is the formula for a line where M represents the slope and B 8 represents the Y intercept. And we're also going to need to use the slope 9 formula, which I for in over here on the right, 10 in which you can input two coordinates to figure out the slope of the 11 line. So we're going to start by taking the two, 12 uh, coordinates. We were given one, four and two zero to calculate the 13 slope. So Y two is zero minus Y. 14 One is four X, two is two and X one is one. 15 And when I input that into the slope formula, 16 that gives me negative four over one or negative four. 17 So now that I know now I know that the slope of the line 18 is negative four, and I can start to write out my equation. 19 So I know that it's going to be, Y is equal to negative four 20 X plus B, where B is the Y intercept now to solve for B, 21 which is what this question is asking for. I can just input any coordinate, 22 uh, into this equation. So I'm going to take to zero. 23 The coordinate that we know is, uh, a point on this line and I'm 24 going to plug that in for X and Y. And 25 now that can solve for B. So I have zero is equal to negative 26 eight plus B. And when I add eight to both sides, 27 I get eight is equal to B. So I know that the correct answer 28 is.