All ACT Math Resources
Example Questions
Example Question #12 : Quadratic Equations
Solve for x.
3x2 + 15x – 18 = 0.
x = –6 or x = 1
x = 5 or x = 1
x = 2 or x = –3
x = –2 or x = 3
x = 6 or x = –1
x = –6 or x = 1
First let's see if there is a common term.
3x2 + 15x – 18 = 0
We can pull out a 3: 3(x2 + 5x – 6) = 0
Divide both sides by 3: x2 + 5x – 6 = 0
We need two numbers that sum to 5 and multiply to –6. 6 and –1 work.
(x + 6)(x – 1) = 0
x = –6 or x = 1
Example Question #15 : How To Find The Solution To A Quadratic Equation
The expression is equal to 0 when and
Factor the expression and set each factor equal to 0:
Example Question #21 : Quadratic Equations
Two positive consecutive multiples of four have a product of 96. What is the sum of the two numbers?
Let = the first number and = the second number.
So the equation to solve becomes . This quadratic equation needs to be multiplied out and set equal to zero before factoring. Then set each factor equal to zero and solve. Only positive numbers are correct, so the answer is .
Example Question #241 : Algebra
Two consecutive positive odd numbers have a product of 35. What is the sum of the two numbers?
Let = first positive number and = second positive number.
The equation to solve becomes
We multiply out this quadratic equation and set it equal to 0, then factor.
Example Question #18 : How To Find The Solution To A Quadratic Equation
The product of two consecutive positive multiples of four is 192. What is the sum of the two numbers?
Let = the first positive number and = the second positive number
The equation to solve becomes
We solve this quadratic equation by multiplying it out and setting it equal to 0. The next step is to factor.
Example Question #22 : Quadratic Equations
Two consecutive positive multiples of three have a product of 504. What is the sum of the two numbers?
Let = the first positive number and = the second positive number.
So the equation to solve is
We multiply out the equation and set it equal to zero before factoring.
thus the two numbers are 21 and 24 for a sum of 45.
Example Question #291 : Equations / Inequalities
Two consecutive positive numbers have a product of 420. What is the sum of the two numbers?
Let = first positive number and = second positive number
So the equation to solve becomes
Using the distributive property, multiply out the equation and then set it equal to 0. Next factor to solve the quadratic.
Example Question #292 : Equations / Inequalities
A rectangle has a perimeter of and an area of What is the difference between the length and width?
For a rectangle, and where = width and = length.
So we get two equations with two unknowns:
Making a substitution we get
Solving the quadratic equation we get or .
The difference is .
Example Question #25 : Quadratic Equations
If then which of the following is a possible value for ?
Since , .
Thus
Of these two, only 4 is a possible answer.
Example Question #141 : Equations / Inequalities
Find all real solutions to the equation.
To solve by factoring, we need two numbers that add to and multiply to .
In order for the equation to equal zero, one of the terms must be equal to zero.
OR
Our final answer is that .
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