Math  /  Algebra

Question2. Find all real solutions of the equation: x210x+21=0x^{2}-10 x+21=0. A. 1 and 21 B. -5 and -5 C. 3 and 7 (x7)(x3)=0(x-7)(x-3)=0

Studdy Solution

STEP 1

What is this asking? We need to find the values of xx that make the equation x210x+21=0x^2 - 10x + 21 = 0 true. Watch out! There might be more than one solution, so don't stop after finding just one!
Also, make sure your solutions actually work when you plug them back into the original equation.

STEP 2

1. Factor the quadratic
2. Solve for x

STEP 3

We're dealing with a **quadratic equation** here, which means it has an x2x^2 term.
A common way to solve these is by **factoring**.
We want to rewrite our equation in the form (xa)(xb)=0(x - a) \cdot (x - b) = 0, where aa and bb are numbers we need to figure out!

STEP 4

We need two numbers that **add up** to 10-10 (the coefficient of our xx term) and **multiply** to 2121 (the constant term).
Think think think... How about 3-3 and 7-7?
Let's check: (3)+(7)=10(-3) + (-7) = -10 and (3)(7)=21(-3) \cdot (-7) = 21.
Perfect!

STEP 5

So, we can rewrite our original equation as (x3)(x7)=0(x - 3)(x - 7) = 0.
Look at that beautiful factoring!

STEP 6

Now, here's a cool trick called the **zero product property**: if two things multiplied together equal zero, then at least one of those things *must* be zero.
So, either (x3)=0(x - 3) = 0 or (x7)=0(x - 7) = 0.

STEP 7

If x3=0x - 3 = 0, then we can **add** 33 to both sides of the equation to **isolate** xx.
This gives us x3+3=0+3x - 3 + 3 = 0 + 3, which simplifies to x=3x = 3.
Boom! Our **first solution** is x=3x = 3.

STEP 8

If x7=0x - 7 = 0, we do the same thing. **Add** 77 to both sides: x7+7=0+7x - 7 + 7 = 0 + 7, which simplifies to x=7x = 7.
Awesome! Our **second solution** is x=7x = 7.

STEP 9

The solutions to the equation x210x+21=0x^2 - 10x + 21 = 0 are x=3x = 3 and x=7x = 7.
So the answer is C!

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