ShmoopTube

Where Monty Python meets your 10th grade teacher.

Search Thousands of Shmoop Videos


Quadratic Equations Videos 11 videos

SAT Math 9.4 Algebra and Functions
1300 Views

SAT Math 9.4 Algebra and Functions

Using the Discriminant
9116 Views

The discriminant is part of the quadratic formula, but that doesn't mean it isn't important in its own right; in fact, once it even guest-hosted Th...

Solving Quadratic Equations Using the Quadratic Formula
4710 Views

To solve using the quadratic equation, you need to find your a, b, and c values. Once you have that, just plug them into the formula, simplify, and...

See All

SAT Math 9.4 Algebra and Functions 1300 Views


Share It!


Description:

SAT Math 9.4 Algebra and Functions

Language:
English Language

Transcript

00:02

Hope you left room for an extra helping of Shmoop.

00:05

If 3x squared + 5x = 12 and x is not an integer, then what must x be?

00:14

All right, so this question looks simple enough.

00:16

We have to find the solution to this equation where x ISN’T an integer.

00:20

So, first we can move 12 to the left side to get 3x squared + 5x – 12 = 0.

00:26

This format look familiar to ya?

00:28

Well, it really doesn’t look like we can factor this one, so let’s apply the quadratic formula.

00:35

So with 3 as a, 5 as b and negative 12, guest starring as c…we can now apply our formula.

00:42

Negative 5 plus or minus radical 25 plus negative 4 times 3 times negative 12…equals 144 all over 6.

00:50

…and 144 plus 25 is 169…ooh, magic number…

00:55

…so we have negative 5 plus or minus 13…all over 6.

01:00

Now we can just separate out the two plus or minus options…

01:04

…and we have negative 5 plus 13 over 6 and negative 5 minus 13 over 6.

01:11

The first one simplifies to 8 over 6, or just 4/3…

01:15

…and the second one simplifies to negative 18 over 6, or just negative 3.

01:19

So, since the question asks us for the non-integer solution to the equation,

01:24

we can forget about that last one.

01:26

Later, negative 3. So yeah…the answer is 4/3.

Related Videos

SAT Math 2.1 Geometry and Measurement
2779 Views

SAT Math 2.1 Geometry and Measurement. What is the measure of angle z in terms of x and y?

SAT Math 9.2 Algebra and Functions
377 Views

SAT Math 9.2 Algebra and Functions

SAT Math: Identifying an Equation for the Average of Two Percentages
23 Views

In 2014, the unemployment rate of one county in California was 7%. In another county, the unemployment rate was 11%. Which of the following express...

SAT Math: Which Equation Represents Profit?
13 Views

Angela is making cookies for a bake sale. She expects each batch of her cookies to sell for $40. It costs her $10 to make one batch of cookies, and...

SAT Math: Using Time and Distance to Calculate Speed
14 Views

Liz leaves her home to drive on a straight highway that leads directly across town for a job interview. At 8:00 a.m., she has driven 5 miles from h...