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# Equation practice with midpoints

Given an information about the distance of a segment's midpoint from its endpoints, Sal forms and solves an equation in order to find the length of the segment. Created by Sal Khan.

## Want to join the conversation?

• how do you find the end point B if they give you the coordinates to A and the midpoint M
eg. A(7,-3) M(1,-1) find the endpoint B
• First multiply the midpoint by 2 getting you (2,-2) then subtract the midpoint from A for x 7-2 and y -3--2, the difference (5, -1) is B
• Around , 8x - 7x = x? I assume the missing 1 is just a place holder?
• why are the subtitles Japanese.
• Did you try changing the language of the subtitles?
• Wait, 8x - 7x would be 1 so wouldn't x be 3 instead of 2 ?
• X X X X X X X X - X X X X X X X = X
That's why X is equal to 2 in this example
We subtracting seven X'es from eight X'es and getting only one X left. 7 and 8 is just a multiplier.
(1 vote)
• So, what if the question gave you the length of JK and JL. What would you do than?
• Well, in this case, both JK and KL are equal, KL would just be JK. But if they weren't, it's just basic subtraction. You subtract the one side you know (JK) from the total length (JL) and get the remaining side (KL).
• Why did you subtract -7x+8 from 8x-8 ..?
(1 vote)
• He knew that 8x-8=7x-6 and he was trying to put all the variables on one side and all the numbers on another side so that he could get x and solve for the total segment
• What if we have the 2 sublengths but we need to find out IF the middle point is actually the midpoint?
• if the three points are in the same line AND the sublengths are equal, it's indeed the midpoint
• in this video, Sal only explains what to do when you have to subtract. What do you do when you need to add such as: `4x + 7 = 3x + 14` ?