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Use the zero product property to find the solutions to the equation x2 + 12 = 7x.

x = –4 or x = 3
x = –4 or x = –3
x = –3 or x = 4
x = 3 or x = 4

2 Answers

6 votes

Answer: D

Explanation:

User Igor Kustov
by
8.3k points
5 votes

Answer:

In a product like:

a*b = 0

says that one of the two terms (or both) must be zero.

Here we have our equation:

x^2 + 12 = 7x

x^2 + 12 - 7x = 0

Let's try to find an equation like:

(x - a)*(x - b) such that:

(x - a)*(x - b) = x^2 + 12 - 7x

we get:

x^2 - a*x - b*x -a*-b = x^2 - 7x + 12

subtracting x^2 in both sides we get:

-(a + b)*x + a*b = -7x + 12

from this, we must have:

-(a + b) = -7

a*b = 12

from the first one, we can see that both a and b must be positive.

Then we only care for the option with positive values, which is x =3 or x = 4

replacing these in both equations, we get:

-(3 + 4) = -7

3*4 = 12

Both of these equations are true, then we can write our quadratic equation as:

(x - 3)*(x - 4) = x^2 + 12 - 7x

The correct option is the last one.

User Tom Shane
by
8.3k points

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