1. **State the problem:** Find the points of intersection for each system of linear equations given.
2. **Recall the method:** The point of intersection of two lines $y=m_1x+b_1$ and $y=m_2x+b_2$ is found by setting the equations equal: $$m_1x+b_1 = m_2x+b_2$$ and solving for $x$, then substituting back to find $y$.
3. **Solve each system:**
**System 1:**
$$y=2x+1$$
$$y=x+3$$
Set equal: $$2x+1 = x+3$$
Subtract $x$ both sides: $$\cancel{2x}+1 = \cancel{x}+3 \Rightarrow x+1=3$$
Subtract 1: $$x=2$$
Find $y$: $$y=2(2)+1=4+1=5$$
Point: $(2,5)$
**System 2:**
$$y=x+3$$
$$y=-3x-2$$
Set equal: $$x+3 = -3x-2$$
Add $3x$: $$x+3x+3 = -3x+3x-2 \Rightarrow 4x+3 = -2$$
Subtract 3: $$4x = -5$$
Divide by 4: $$\frac{4x}{\cancel{4}} = \frac{-5}{\cancel{4}} \Rightarrow x = -\frac{5}{4}$$
Find $y$: $$y = -\frac{5}{4} + 3 = -\frac{5}{4} + \frac{12}{4} = \frac{7}{4}$$
Point: $\left(-\frac{5}{4}, \frac{7}{4}\right)$
**System 3:**
$$y = -x - 7$$
$$y = x + 3$$
Set equal: $$-x - 7 = x + 3$$
Add $x$: $$-x + x - 7 = x + x + 3 \Rightarrow -7 = 2x + 3$$
Subtract 3: $$-10 = 2x$$
Divide by 2: $$\frac{-10}{\cancel{2}} = \frac{2x}{\cancel{2}} \Rightarrow x = -5$$
Find $y$: $$y = -(-5) - 7 = 5 - 7 = -2$$
Point: $(-5, -2)$
**System 4:**
$$y = -x - 7$$
$$y = 2x + 1$$
Set equal: $$-x - 7 = 2x + 1$$
Add $x$: $$-x + x - 7 = 2x + x + 1 \Rightarrow -7 = 3x + 1$$
Subtract 1: $$-8 = 3x$$
Divide by 3: $$\frac{-8}{\cancel{3}} = \frac{3x}{\cancel{3}} \Rightarrow x = -\frac{8}{3}$$
Find $y$: $$y = 2\left(-\frac{8}{3}\right) + 1 = -\frac{16}{3} + 1 = -\frac{16}{3} + \frac{3}{3} = -\frac{13}{3}$$
Point: $\left(-\frac{8}{3}, -\frac{13}{3}\right)$
**System 5:**
$$y = 2x + 1$$
$$y = -3x - 2$$
Set equal: $$2x + 1 = -3x - 2$$
Add $3x$: $$2x + 3x + 1 = -3x + 3x - 2 \Rightarrow 5x + 1 = -2$$
Subtract 1: $$5x = -3$$
Divide by 5: $$\frac{5x}{\cancel{5}} = \frac{-3}{\cancel{5}} \Rightarrow x = -\frac{3}{5}$$
Find $y$: $$y = 2\left(-\frac{3}{5}\right) + 1 = -\frac{6}{5} + 1 = -\frac{6}{5} + \frac{5}{5} = -\frac{1}{5}$$
Point: $\left(-\frac{3}{5}, -\frac{1}{5}\right)$
4. **Final answers:**
- System 1: $(2,5)$
- System 2: $\left(-\frac{5}{4}, \frac{7}{4}\right)$
- System 3: $(-5,-2)$
- System 4: $\left(-\frac{8}{3}, -\frac{13}{3}\right)$
- System 5: $\left(-\frac{3}{5}, -\frac{1}{5}\right)$
Linear Systems 40F741
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