### SAT数学：代数例题 7

2019-08-29 SAT-数学 阅读

# SAT Question 9 Article Rank: Medium 难度： 中等 Topic: Algebra, Equation of a line 话题：代数，直线公式

Below is a question from a recent SAT exam. It is a non-calculator question that would typically take a student 1-2 minutes to complete. Which of the following is an equation of line in the
xy-plane above? To begin, we must recall that the equation on a straight line comes in the form Where m is the slope and c is the y-intercept.

We will start by finding the y-intercept. This is the point where the line crosses the y-axis. We can clearly see in this diagram that the line meet the y-axis at -4. So we can replace c in our equation. Now we need to find the slope of the line. To find this we use the formula: So we need to find to point on our line, any two will do but, I will pick the two points where it meets an axis.

(0, -4) & (-4,0)

So our two x-coordinates are 0 and -4 whilst our two y-coordinates are -4 and 0.
We can put these into the formula: Therefore, We put this now into our equation for our line. We then can move x to the LHS of the equation. And we can see that the answer is C. • 地址：401-5811 Cooney Rd, Richmond, BC
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