Math 7 · Unit 4, Lesson 3: Expanding · Tile 2 of 3
Negatives Get a Turn Too
Minus signs inside and outside
Minus signs inside and outside
When there's subtraction inside, change it to adding the opposite first, like Lesson 1, Tile 2. When the number outside is negative, it multiplies every term inside too, and the signs follow the rules from Unit 3: same signs, positive, and different signs, negative.
−2 times −7 is positive 14. Same signs, positive.
Elle and Finn
When distributing a negative factor, multiply each term by the negative number. The sign of each product follows the rules for multiplying signed numbers.
A negative out front flips the sign of every term inside. Positive terms turn negative, and negative terms turn positive.
Elle and Finn talk it over
A negative out front is like a grumpy cookie hander.
How so?
Every kid still gets a cookie. But now the cookie is sad.
And the kids who were already sad?
Two sads make a happy. Unit 3 told me.
Only because we are multiplying.
That is real math. −2(3y − 7) = −6y + 14, because −2 × (−7) = 14.
NC standards: NC.7.EE.1, NC.7.NS.2.