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Rewrite the expression five
times 9 minus 4-- that's in
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parentheses-- using the
distributive law of
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multiplication over
subtraction.
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Then simplify.
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So let me just rewrite it.
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This is going to be 5 times
9 minus 4, just like that.
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Now, if we want to use the
distributive property, well,
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you don't have to.
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You could just evaluate
9 minus 4 and then
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multiply that times 5.
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But if you want to use the
distributive property, you
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distribute the 5.
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You multiply the 5 times the 9
and the 4, so you end up with
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5 times 9 minus 5 times 4.
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Notice, we distributed the 5.
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We multiplied it times
both the 9 and the 4.
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In the first distributive
property video, we gave you an
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idea of why you have to
distribute the 5, why it makes
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sense, why you don't just
multiply it by the 9.
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And we're going to verify that
it gives us the same answer as
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if we just evaluated the 9 minus
4 first. But anyway,
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what are these things?
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So 5 times 9, that is 45.
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So we have 45 minus--
what's 5 times 4?
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Well, that's 20.
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45 minus 20, and that is equal
to 25, so this is using the
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distributive property
right here.
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If we didn't want to use the
distributive property, if we
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just wanted to evaluate what's
in the parentheses first, we
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would have gotten-- let's go in
this direction-- 5 times--
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what's 9 minus 4?
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9 minus 4 is 5.
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Let me do that in a
different color.
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5 times 9 minus 4.
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So it's 5 times 5.
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5 times 5 is just 25,
so we get the same
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answer either way.
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This is using the distributive
law of multiplication over
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subtraction, usually just
referred to as the
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distributive property.
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This is evaluating the inside
of the parentheses first and
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then multiplying by 5.
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