聯立不等式 2 (英)
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- Solve for y.
- We have three y plus seven is less than two y and
- four y plus eight is greater than negative forty-eight.
- So we have to find all the y's that meet both of these constraints
- so let's just solve for y in each of the constraints and just remember that this "and" is here.
- So we have three y plus seven is less than two y
- so let's isolate the y's on the left-hand side
- so let's get rid of this two y on the right-hand side
- and we can do that by subtracting two y from both sides.
- So we're going to subtract two y from both sides,
- the left-hand sides we have three y minus two y,
- which is just y, plus seven
- is less than two y minus two y and there's nothing else there
- that's just going to be zero.
- And then we can get rid of this seven here
- by subtracting seven from both sides
- so let's subtract seven from both sides,
- left-hand side, y plus seven minus seven, those cancel out, we just have a y
- is less than zero minus seven, which is negative seven.
- so that's one of the constraints. That's this constraint
- right over here.
- Now let's work on this constraint.
- We have four y, plus eight is greater than negative forty-eight.
- So let's get rid of the eight from the left-hand side
- so we can subtract eight from both sides, subtract eight from both sides,
- the left-hand side we're just left with a four y because
- these guys cancel out.
- Four y is greater than negative forty-eight minus eight
- So we're going to go another eight negative,
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