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Video transcript

evaluate 3x squared minus 8x plus seven when X is equal to negative two so to evaluate this expression when X is equal to negative two everywhere that we see an X we just have to substitute it with a negative two so it would be three times instead of x squared would be three times negative two squared minus eight times instead of eight times X eight times negative two plus seven and so what does this give us so we have three times negative two squared well that's just positive 4 negative times a negative is a positive minus 8 times negative 2 is negative 16 negative 16 plus 7 so 3 times 4 is 12 your sum from that you're subtracting negative 16 subtracting negative 16 is the same thing as adding positive 16 so it's 12 plus 16 plus 7 and so this is equal to 12 plus 16 is 28 and then if you add 7 to 28 you get you get 35