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Current time:0:00Total duration:1:35

Video transcript

so we're told it's a pillow is a plus B is equal to zero which of these expressions equal a times B and like always pause the video and see if you can figure it out these these are actually pretty fun problems alright so let's see if we can do a little bit of manipulation so we weren't told that a plus B is equal to zero so if we subtract B from both sides we would get so if I subtract B from both sides I would get a is equal to negative B so what is a times B equal to so a times B well I could write this a few ways I could substitute the a with a negative B since we know a is equal to negative B in which case in which case a times B would be negative B times B which is equal to negative B squared another option is I could I could I could instead of saying a is equal to negative B I could say that B is equal to negative a if we multiply both sides times negative one so B is equal to negative a and so I could stead of substituting a I could substitute B with negative a and so this expression would be a times negative a a times negative a which is equal to negative a squared so let's see which of these choices are there there's a B squared but not negative B squared so we see the negative a squared right over there so I'm feeling good I'm feeling good about that choice