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#### Mathematics 3 ESO – Unit 7 SYSTEMS OF LINEAR EQUATIONS Page 61 – Activity 33

1. a) Watch the video on “Solving Simultaneous Equations by Graph” and answer:
2. I)What means that simultaneous equations can be solved graphically?
3. II)Why are the equations in the example “linear equations”?

III)  Why the points that we find to draw the lines are always on the axis?

1. IV)After drawing the two lines, how do we find the solution to the system?
2. V)Using a graphical method, can we always rely on being totally accurate? Why do you think that is?
1. b)Watch the video on “Solving Simultaneous Equations by Elimination” and answer:
2. I)Why do we want to find values of “x”?
3. II)When we have the same number of “y’s”, why do we subtract the equations (not add them)?

III) When we have found the value of “x”, in what equation do we have to substitute the value of “x”?

1. IV)How do we check that the solutions are correct?
1. c) Watch the video on “Solving Simultaneous Equations by Substitution” and answer:
2. I)When we use substitution, how do we combine both equations?
3. II)Solve this system by substitution: x = 4y – 10  ;  2x + 5y = 6 and check the solutions.
1. d) Scroll down to the interactive window and play with theblue lines by moving the points on the lines. The red point is the solution.
2. I)What is the solution if the points on one line are (-2,3) and (2,3) and the points on the other line are (3,1) and (3,-2)?
3. II)What is the solution if the points on one line are (-2,3) and (2,3) and the points on the other line are (1,0) and (3,-2)?