M
Math Coach Amy
Amy Ferguson Moncure

SAT

Exactly One Solution

Solve for x. Find the equation with exactly one solution.

Jump to section:

What to Remember

Solve for x.

Get all the variables on one side and all the numbers on the other side.

If x equals a number, there is exactly one solution. Any number counts.

x equals a number

4x + 3=x + 12
3x + 3=12
3x=9
x=3

x = 3. There is exactly one solution.

x = 0

6x + 2=2x + 2
4x + 2=2
4x=0
x=0

x = 0 is a number.

Infinite solutions

4x + 5=4x + 5
5=5

5 = 5. Math Truth! Infinite solutions.

No solution

2x + 3=2x + 7
3=7

3 = 7. Math Lie! No Solutions.

Together

Together

Work these three in a session.

1

Which equation has exactly one solution?

A. 4x + 9 = 4x + 2 B. 6x + 5 = 6x + 5 C. 5x + 1 = 2x + 13 D. 3x − 4 = 3x + 7
Show Answer
A.4x + 9=4x + 2
9=2
Math Lie! No Solution
B.6x + 5=6x + 5
5=5
Math Truth! Infinite Solution!
C.5x + 1=2x + 13
3x + 1=13
3x=12
x=4
One Solution!
D.3x − 4=3x + 7
−4=7
Math Lie! No Solution

Answer: C. 5x + 1 = 2x + 13

2

Which equation has exactly one solution?

A. 8x + 5 = 3x + 5 B. 8x + 3 = 8x − 6 C. x + 9 = x + 9 D. 5x + 2 = 5x + 14
Show Answer
A.8x + 5=3x + 5
5x + 5=5
5x=0
x=0
One Solution!
x = 0 is exactly one solution. Zero is a number.
B.8x + 3=8x − 6
3=−6
Math Lie! No Solution
C.x + 9=x + 9
9=9
Math Truth! Infinite Solution!
D.5x + 2=5x + 14
2=14
Math Lie! No Solution

Answer: A. 8x + 5 = 3x + 5

3

Which equation has exactly one solution?

A. 7x − 3 = 7x − 3 B. 4x + 6 = 4x + 1 C. 9x + 8 = 9x − 2 D. 6x − 5 = 2x + 7
Show Answer
A.7x − 3=7x − 3
−3=−3
Math Truth! Infinite Solution!
B.4x + 6=4x + 1
6=1
Math Lie! No Solution
C.9x + 8=9x − 2
8=−2
Math Lie! No Solution
D.6x − 5=2x + 7
4x − 5=7
4x=12
x=3
One Solution!

Answer: D. 6x − 5 = 2x + 7

Independent

Independent Practice

Try these five on your own.

1

Which equation has exactly one solution?

A. 2x − 7 = 2x + 5 B. 8x − 4 = 2x + 8 C. 6x + 1 = 6x + 1 D. 4x + 10 = 4x − 8
Show Answer
A.2x − 7=2x + 5
−7=5
Math Lie! No Solution
B.8x − 4=2x + 8
6x − 4=8
6x=12
x=2
One Solution!
C.6x + 1=6x + 1
1=1
Math Truth! Infinite Solution!
D.4x + 10=4x − 8
10=−8
Math Lie! No Solution

Answer: B. 8x − 4 = 2x + 8

2

Which equation has exactly one solution?

A. 5x + 6 = 5x + 6 B. 3x − 9 = 3x + 2 C. 7x + 4 = 7x − 1 D. 5x − 6 = 2x − 6
Show Answer
A.5x + 6=5x + 6
6=6
Math Truth! Infinite Solution!
B.3x − 9=3x + 2
−9=2
Math Lie! No Solution
C.7x + 4=7x − 1
4=−1
Math Lie! No Solution
D.5x − 6=2x − 6
3x − 6=−6
3x=0
x=0
One Solution!
x = 0 is exactly one solution. Zero is a number.

Answer: D. 5x − 6 = 2x − 6

3

Which equation has exactly one solution?

A. −5x + 4 = x + 16 B. −4x + 7 = −4x + 2 C. −6x − 1 = −6x − 1 D. 5x + 8 = 5x − 3
Show Answer
A.−5x + 4=x + 16
−6x + 4=16
−6x=12
x=−2
One Solution!
B.−4x + 7=−4x + 2
7=2
Math Lie! No Solution
C.−6x − 1=−6x − 1
−1=−1
Math Truth! Infinite Solution!
D.5x + 8=5x − 3
8=−3
Math Lie! No Solution

Answer: A. −5x + 4 = x + 16

4

Which equation has exactly one solution?

A. 9x + 4 = 9x + 4 B. 2x − 5 = 2x + 11 C. 7x − 6 = 4x + 9 D. −3x + 8 = −3x − 4
Show Answer
A.9x + 4=9x + 4
4=4
Math Truth! Infinite Solution!
B.2x − 5=2x + 11
−5=11
Math Lie! No Solution
C.7x − 6=4x + 9
3x − 6=9
3x=15
x=5
One Solution!
D.−3x + 8=−3x − 4
8=−4
Math Lie! No Solution

Answer: C. 7x − 6 = 4x + 9

5

Which equation has exactly one solution?

A. 6x − 8 = 6x + 4 B. 6x − 8 = 2x + 12 C. 6x − 8 = 6x − 8 D. 2x + 12 = 2x − 8
Show Answer
A.6x − 8=6x + 4
−8=4
Math Lie! No Solution
B.6x − 8=2x + 12
4x − 8=12
4x=20
x=5
One Solution!
C.6x − 8=6x − 8
−8=−8
Math Truth! Infinite Solution!
D.2x + 12=2x − 8
12=−8
Math Lie! No Solution

Answer: B. 6x − 8 = 2x + 12

Want to practice this together?

Book a Session with Amy