Question

ii.
Verify whether -1 is the root of quadratic equation
${x}^{2} + 4x - 5 = 0$
​

Answer 1

Answer:

-1 is not teh root of the quadratic equation

Answer 2

Answer:

Solve the equation by completing the square

x^2 + 4x - 21 = 0

Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

x%5E2%2B4x-21=0 Start with the given equation

x%5E2%2B4x=21 Add 21 to both sides

Take half of the x coefficient 4 to get 2 (ie 4%2F2=2)

Now square 2 to get 4 (ie %282%29%5E2=4)

x%5E2%2B4x%2B4=21%2B4 Add this result (4) to both sides. Now the expression x%5E2%2B4x%2B4 is a perfect square trinomial.

%28x%2B2%29%5E2=21%2B4 Factor x%5E2%2B4x%2B4 into %28x%2B2%29%5E2 (note: if you need help with factoring, check out this solver)

%28x%2B2%29%5E2=25 Combine like terms on the right side

x%2B2=0%2B-sqrt%2825%29 Take the square root of both sides

x=-2%2B-sqrt%2825%29 Subtract 2 from both sides to isolate x.

So the expression breaks down to

x=-2%2Bsqrt%2825%29 or x=-2-sqrt%2825%29

x=-2%2B5 or x=-2-5 Take the square root of 25 to get 5

x=3 or x=-7 Now combine like terms

So our answer is

x=3 or x=-7

Here is visual proof