Solve for X: Finding the Value in (x+3)² = x² + 15

What is the value of x?

(x+3)2=x2+15 (x+3)^2=x^2+15

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:03 Use abbreviated multiplication formulas to open the brackets
00:10 Solve the multiplications and squares
00:18 Simplify what we can
00:23 Isolate X
00:39 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

What is the value of x?

(x+3)2=x2+15 (x+3)^2=x^2+15

2

Step-by-step solution

Let's solve the equation, first we'll simplify the algebraic expressions using the perfect square binomial formula:

(a±b)2=a2±2ab+b2 (a\pm b)^2=a^2\pm2ab+b^2 We will then apply the mentioned formula and expand the parentheses in the expression in the equation:

(x+3)2=x2+15x2+2x3+32=x2+15x2+6x+9=x2+15 (x+3)^2=x^2+15 \\ x^2+2\cdot x\cdot3+3^2=x^2+15\\ x^2+6x+9=x^2+15 We'll continue and combine like terms, by moving terms between sides. Then we can notice that the squared term cancels out, therefore it's a first-degree equation, which we'll solve by isolating the variable term on one side and dividing both sides of the equation by its coefficient:

x2+6x+9=x2+156x=6/:6x=1 x^2+6x+9=x^2+15 \\ 6x=6\hspace{8pt}\text{/}:6\\ \boxed{x=1} Therefore, the correct answer is answer B.

3

Final Answer

x=1 x=1

Practice Quiz

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Choose the expression that has the same value as the following:

\( (x+y)^2 \)

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