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Absolute value measures distance, which is why one equation can send you in two directions. The bars do not mean “make everything positive.” They ask how far the expression inside sits from zero, or from another center after a graph has shifted.
On the SAT, |x| is the distance from x to 0. Solve |ax+b|=c by setting the inside equal to c and -c, translate inequalities as inside or outside a distance boundary, and read y=|x-h|+k as a V with vertex (h,k).
Key takeaways
- |x| is distance from 0, so it is always nonnegative.
- If c>0, then |ax+b|=c creates two linear cases: ax+b=c or ax+b=-c.
- |ax+b|<c describes values inside a distance boundary; |ax+b|>c describes values outside it.
- y=|x-h|+k is V-shaped with vertex (h,k) and symmetry line x=h.
- Check the sign of c before splitting. A negative distance can make an equation or inside inequality impossible.
What does absolute value mean on the SAT?
Distance has no sign. Both 5 and -5 sit 5 units from 0, so |5|=5 and |-5|=5. More generally, |x-a| is the distance from x to a. The statement |x-4|=3 therefore asks for the two points 3 units from 4: x=7 and x=1.
|u|=c means “the distance of u from 0 is c.” That sentence explains the two cases, the inequality splits, and the V-shaped graph without requiring three unrelated rules.
How do you solve an absolute-value equation?
- 1
Isolate the bars
Rewrite until the absolute-value expression stands alone. For example, 2|3x-1|=10 becomes |3x-1|=5.
- 2
Check the distance
If the right side is negative, there is no solution. If it is 0, the inside must equal 0. If it is positive, continue with two cases.
- 3
Split
Set the inside equal to both values: 3x-1=5 or 3x-1=-5.
- 4
Solve and verify
The cases give x=2 and x=-\frac{4}{3}. Substitute each into the original equation.
The case equations use the same balance moves as linear equations and inequalities. The extra work happens before the linear solving: isolate the bars, inspect the right side, and create every legal case.
How do absolute-value inequalities split?
| Form with c>0 | Distance meaning | Equivalent statement |
|---|---|---|
| |u|<c | Inside the boundary | -c<u<c |
| |u|\le c | Inside or on the boundary | -c\le u\le c |
| |u|>c | Outside the boundary | u<-c or u>c |
| |u|\ge c | Outside or on the boundary | u\le -c or u\ge c |
For |2x+1|<7, write -7<2x+1<7, subtract 1 across the chain, and divide by 2 to get -4<x<3. For |2x+1|>7, write two outside cases: 2x+1<-7 or 2x+1>7, giving x<-4 or x>3. If an inequality operation multiplies or divides by a negative, reverse the affected signs as usual.
How do you read an absolute-value graph?
The parent graph y=|x| has vertex (0,0) and rises with slopes -1 and 1 on its two arms. In y=a|x-h|+k, the vertex moves to (h,k). The value of |a| changes steepness, and a negative a opens the V downward. The nonlinear-equations guide connects absolute-value intersections with other nonlinear systems.
Forgotten case
Solve only ax+b=c because the absolute value appears positive.
Distance cases
After confirming c>0, solve ax+b=c and ax+b=-c, then verify both results.
Can you solve one SAT absolute-value question?
Which solution set satisfies |3x-5|>7?
Absolute value sits between linear solving and nonlinear graph shape. The SAT Math strategies guide helps decide when algebra, a number line, or a graph is the cleanest representation.
Use distance language to solve the cases, then connect each solution set to the V-shaped graph.
Practice nonlinear functions →Frequently asked questions
- What does absolute value mean on the SAT?
- Absolute value is distance from zero. More generally, the absolute value of x minus a measures the distance from x to a, so it can describe two symmetric locations.
- Why do absolute-value equations have two solutions?
- A positive distance can occur on either side of zero. After the absolute-value expression is isolated, its inside can equal the positive distance or the corresponding negative value.
- How do absolute-value inequalities work?
- A less-than inequality describes values inside two boundary points, while a greater-than inequality describes the two outside rays. Check that the distance bound is positive before splitting.
- What does an absolute-value graph look like?
- Its parent graph is V-shaped with a vertex at the origin. Horizontal and vertical shifts move the vertex, the leading coefficient changes steepness, and a negative coefficient opens it downward.