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4 votes
Solve 3x2 + 12x = 3.

−2 ± square root 13
−2 ± square root 7
−2 ± square root 3
−2 ± square root 5

User Guito
by
8.8k points

2 Answers

5 votes
−2 ± square root 5 ....................
User Toodoo
by
8.7k points
1 vote

Answer: The correct option is (D)
x=-2\pm\sqrt5.

Step-by-step explanation: We are given to solve the following quadratic equation :


3x^2+12x=3~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~(i)

We will be using the method of COMPLETING THE SQUARE to solve the given problem where the following square formula is used :


a^2+2ab+b^2=(a+b)^2.

From equation (i), we have


3x^2+12x=3\\\\\Rightarrow 3(x^2+4x)=3\\\\\Rightarrow x^2+4x=1\\\\\Rightarrow x^2+2* x*2+2^2=1+2^2\\\\\Rightarrow (x+2)^2=1+4\\\\\Rightarrow (x+2)^2=5\\\\\Rightarrow x+2=\pm\sqrt5~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~[\textup{taking square root on both sides}]\\\\\Rightarrow x=-2\pm\sqrt5.

Thus, the required solution of the given quadratic equation is


x=-2\pm\sqrt5.

Option (D) is CORRECT.

User Shashank Sawant
by
7.6k points

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