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We're asked to evaluate the expression a squared plus ten b minus eight when a is equal to seven and b is equal to negative four.

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So to evaluate the expression we really just need to substitute a with 7 and substitute b with negative 4.

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Because they are saying evaluate it when a is seven and b is negative four. So let's do that.

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So everywhere we see an a in the expression we should put a seven there. So instead of a squared

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we should write seven squared plus ten times b. But instead of a b there we are

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now going to substitute it with b is equal to negative four. So ten times negative four instead of the

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b right over there. And then we have the minus eight. And now we just have to evaluate this thing.

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Seven squared is forty-nine. And then ten times negative four, remember order of operations.

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Multiplication comes before addition so we have to multiply this. Ten times negative four is

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negative forty. So it's plus negative forty, and then we have minus eight over here.

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And so we get forty-nine plus negative forty, which is the same thing as forty-nine minus forty, is going

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to be nine. Then we're going to subtract eight from that. And so we get one.

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Forty-nine minus forty is nine, and minus eight is one. We are done.

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We have evaluated the expression when a is equal to seven and b is equal to negative four.