Question
Find the roots
y1=21−5,y2=21+5
Alternative Form
y1≈−0.618034,y2≈1.618034
Evaluate
y2−y−1
To find the roots of the expression,set the expression equal to 0
y2−y−1=0
Substitute a=1,b=−1 and c=−1 into the quadratic formula y=2a−b±b2−4ac
y=21±(−1)2−4(−1)
Simplify the expression
More Steps

Evaluate
(−1)2−4(−1)
Evaluate the power
1−4(−1)
Simplify
1−(−4)
If a negative sign or a subtraction symbol appears outside parentheses, remove the parentheses and change the sign of every term within the parentheses
1+4
Add the numbers
5
y=21±5
Separate the equation into 2 possible cases
y=21+5y=21−5
Solution
y1=21−5,y2=21+5
Alternative Form
y1≈−0.618034,y2≈1.618034
Show Solution
