How to solve :/?

Question

Find k such that x²+(k+1)x+k+4=0 will have two equal roots.

Answer 1

The equation has two equal roots if the discriminant equals 0

The discriminant is b²-4ac

In your case a=1, b=k+1, c=k+4

Plug those values in the formula for the discriminant...

(k+1)²-4(1)(k+4)=k²+2k+1-4k-16=k²-2k-15

For the discriminant to equal zero k must satisfy the equation k²-2k-15=0

Just solve the equation and you have the values for k.

Hope this helps!