Re: If sqrt 8x^2+17=3x-2
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01 Mar 2026, 12:58
Step-by-Step Solution:
1. Isolate the square root and square both sides:
$$
\(\begin{gathered}
\sqrt{8 x^2+17}=3 x-2 \\
\left(\sqrt{8 x^2+17}\right)^2=(3 x-2)^2
\end{gathered}\)
$$
2. Expand the equation:
$$
\(8 x^2+17=9 x^2-12 x+4\)
$$
3. Move all terms to one side to form a quadratic equation:
Subtract $\(8 x^2\)$ and 17 from both sides:
$$
\(0=x^2-12 x-13\)
$$
4. Factor the quadratic equation:
We look for two numbers that multiply to -13 and add to -12 :
$$
\(0=(x-13)(x+1)\)
$$
So, the potential solutions are:
$$
\(x=13 \quad \text { or } \quad x=-1\)
$$
5. Check for extraneous solutions:
Because we squared both sides, we must verify the solutions in the original equation (specifically, the right side $3 x-2$ must be non-negative).
- Check $\(x=13\)$ :
$$
\(\begin{aligned}
& \text { LHS: } \sqrt{8(13)^2+17}=\sqrt{8(169)+17}=\sqrt{1352+17}=\sqrt{1369}=37 \\
& \text { RHS: } 3(13)-2=39-2=37 \\
& 37=37 \text { (Valid) }
\end{aligned}\)
$$
- Check $\(x=-1\)$ :
$$
\(\begin{aligned}
& \text { LHS: } \sqrt{8(-1)^2+17}=\sqrt{8+17}=\sqrt{25}=5 \\
& \text { RHS: } 3(-1)-2=-3-2=-5 \\
& 5 \neq-5 \text { (Extraneous) }
\end{aligned}\)
$$
6. Final Calculation:
Since $\(x=13\)$ :
$$
\(2 x=2 \times 13=26\)
$$