Linear Systems 97Be5C
1. **State the problem:**
Solve the first system of linear equations:
$$3x - y = 7$$
$$2x + 5y + 1 = 0$$
2. **Rewrite the second equation:**
$$2x + 5y = -1$$
3. **Express $y$ from the first equation:**
$$3x - y = 7 \implies y = 3x - 7$$
4. **Substitute $y$ into the second equation:**
$$2x + 5(3x - 7) = -1$$
$$2x + 15x - 35 = -1$$
$$17x - 35 = -1$$
5. **Solve for $x$:**
$$17x = 34 \implies x = 2$$
6. **Find $y$ using $x=2$:**
$$y = 3(2) - 7 = 6 - 7 = -1$$
7. **Final solution for the first system:**
$$(x, y) = (2, -1)$$
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1. **State the problem:**
Solve the second system of linear equations:
$$x + 3y = 12$$
$$2x - 3y = 12$$
2. **Add the two equations to eliminate $y$:**
$$(x + 3y) + (2x - 3y) = 12 + 12$$
$$3x = 24 \implies x = 8$$
3. **Substitute $x=8$ into the first equation:**
$$8 + 3y = 12 \implies 3y = 4 \implies y = \frac{4}{3}$$
4. **Final solution for the second system:**
$$(x, y) = \left(8, \frac{4}{3}\right)$$
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1. **State the problem:**
Shade the region bounded by the line
$$2x - 3y = 2$$
and the coordinate axes.
2. **Rewrite the line in terms of $y$:**
$$2x - 3y = 2 \implies 3y = 2x - 2 \implies y = \frac{2x - 2}{3}$$
3. **Find intercepts:**
- When $x=0$,
$$y = \frac{2(0) - 2}{3} = -\frac{2}{3}$$ (negative, so no positive intercept on y-axis)
- When $y=0$,
$$2x - 3(0) = 2 \implies x = 1$$
4. **Since the y-intercept is negative, the bounded region with axes and line is a triangle with vertices at:**
$$(0,0), (1,0), \text{and the point where the line crosses the y-axis if positive}$$
5. **Check where the line crosses the y-axis positively:**
Set $x=1$ in the line equation:
$$y = \frac{2(1) - 2}{3} = 0$$
6. **Check the region bounded by the line and axes:**
The line crosses the x-axis at $(1,0)$ and the y-axis at $(0,-\frac{2}{3})$ (below x-axis), so the bounded region is the triangle formed by the x-axis, y-axis, and the line segment from $(0,0)$ to $(1,0)$.
7. **Shade the triangular region bounded by:**
- The x-axis ($y=0$)
- The y-axis ($x=0$)
- The line $2x - 3y = 2$
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**Summary:**
- First system solution: $(2, -1)$
- Second system solution: $(8, \frac{4}{3})$
- Shaded region: triangle bounded by $x=0$, $y=0$, and $2x - 3y = 2$