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No Solution
A system of equations has no solution when the two lines are parallel. This means they:
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Have the same slope
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But different y-intercepts
What the Graph Looks Like
Two lines that never intersect — they just go side-by-side forever.
How to Recognize It
Put both equations into slope-intercept form:
y = mx + b
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If m (slope) is the same but b (y-intercept) is different → no solution
Example:
Equation 1:
Equation 2:
Both linear functions have a slope of 2. Same slope and different y-intercepts, so there’s no solution.
Infinite Solutions
A system of equations has infinite solutions when the two equations represent the same exact line. That means:
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Same slope
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Same y-intercept
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Every point on one line is also on the other
What the Graph Looks Like
It looks like just one line, even though it came from two equations.
How to Recognize It
Again, write both equations in slope-intercept form:
y = mx + b
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If both equations are exactly the same after simplifying → infinite solutions
Example
Equation 1:
Equation 2: → divide everything by 6
→ Same as Equation 1 → Infinite Solutions
Strategy to Solve These on the SAT
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Get both equations into slope-intercept form (
)
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Compare slopes:
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Same slope, different y-intercepts → ❌ No Solution
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Same slope, same y-intercepts → ♾ Infinite Solutions
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Different slopes → ✅ One Unique Solution (the lines intersect once)
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SAT Practice Tip
You can also graph both equations in Desmos:
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If they intersect → one solution
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If they don’t intersect → no solution
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If they overlap → infinite solutions