A straight line goes through (0,1), (2,5) and (4,9). The equation of the straight line is y=2x+1. Is the point (7,12) on this straight line?
- First we'll figure out what the numbers in the co-ordinates mean. On the point (7,12) x= 7 and y=12. - The equation of the line is in the form of y=mx + c so for the point to be on the line, the y value must equal mx + c. - m is our gradient, and in this case is 2. This is given in the question. - c is the y-intercept and we are told that it is 1. - So to find out the value of y, we put our values into the equation y=2(7) + 1... y= 15. - As we get an answer of 15, and not 12 (given in our co-ordinates) we have found out that this point does not lie on the straight line. Therefore, the answer to the question is No. These kind of workings must be shown to fully explain how you came to your answer and to get full marks in a test.
