Solve the equation by completing the square. 0 = 4x2 − 72x
1 answer:
Answer:
B
Step-by-step explanation:
Given
4x² - 72x = 0 ← factor out 4 from each term
4(x² - 18x) = 0
To complete the square
add/subtract (half the coefficient of the x- term)² to x² - 18x
4(x² + 2(- 9)x + 81 - 81) = 0
4(x - 9)² - 4(81) = 0
4(x - 9)² - 324 = 0 ( add 324 to both sides )
4(x - 9)² = 324 ( divide both sides by 4 )
(x - 9)² = 81 ( take the square root of both sides )
x - 9 = ± = ± 9 ( add 9 to both sides )
x = 9 ± 9
Then
x = 9 - 9 = 0
x = 9 + 9 = 18
You might be interested in
Answer:
Step-by-step explanation:
The correct question is
Susan works as a tutor for $10 and hour, and as a waitress for $11 an hour. This month, she worked a combined total of 90 hours at her two jobs. Let t be the number of hours Susan worked as a tutor this month. Write an expression for the combined total dollar amount she earned this month
Let
t -----> the number of hours that Susan work as a tutor
y ----> the number of hours that Susan work as a waitress
z ---> the combined total dollar amount she earned this month
we know that
-----> equation A
we know that
The combined total dollar amount she earned this month is equal to the number of hours that Susan work as a tutor multiplied by $10 plus the number of hours that Susan work as a waitress multiplied by $11
----> equation B
substitute equation A in equation B
therefore
The expression for the combined total dollar amount is $(990-t)