Complete the square for 5x^2+10x-16.
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x= -1 + √(21/5)

Step-by-step explanation:

The given equation can be written as 5x^2+10x-16=0

keep the x terms on one side and constant on another side

5x^2+ 10x = 16.

Now, to make a complete square like (x+a)^2 = x^2+2xa+a^2.

Divide the given equation by 5 on both sides,

The equation now becomes x^2+2x = 16/5.

The middle term is 2xa=2x

By solving for term "a" in above equation, a= 1

The entire equation of complete square should be x^2+2x+1, which is equal to (x+1)^2

Here, in the equation given in question, +1 is missing to make a complete square.

In order to add 1 we have to simultaneously minus 1 to keep the values in the equation unchanged.

Thus, x^2+2x+1-1 =16/5.

Again moving the constant -1 to other side, we have

x^2+2x+1 =16/5+1

After simplification,

(x+1)^2= 21/5

Taking square root on both sides,

(x+1)= + √(21/5)

The answer is x= -1 + √(21/5)