Algebra
Calculus
Trigonometry
Matrix
Question
Factor the expression
(y−21)(y+1)
Evaluate
y2−20y−21
Rewrite the expression
y2+(1−21)y−21
Calculate
y2+y−21y−21
Rewrite the expression
y×y+y−21y−21
Factor out y from the expression
y(y+1)−21y−21
Factor out −21 from the expression
y(y+1)−21(y+1)
Solution
(y−21)(y+1)
Show Solution
Find the roots
y1=−1,y2=21
Evaluate
y2−20y−21
To find the roots of the expression,set the expression equal to 0
y2−20y−21=0
Factor the expression
More Steps
Evaluate
y2−20y−21
Rewrite the expression
y2+(1−21)y−21
Calculate
y2+y−21y−21
Rewrite the expression
y×y+y−21y−21
Factor out y from the expression
y(y+1)−21y−21
Factor out −21 from the expression
y(y+1)−21(y+1)
Factor out y+1 from the expression
(y−21)(y+1)
(y−21)(y+1)=0
When the product of factors equals 0,at least one factor is 0
y−21=0y+1=0
Solve the equation for y
More Steps
Evaluate
y−21=0
Move the constant to the right-hand side and change its sign
y=0+21
Removing 0 doesn't change the value,so remove it from the expression
y=21
y=21y+1=0
Solve the equation for y
More Steps
Evaluate
y+1=0
Move the constant to the right-hand side and change its sign
y=0−1
Removing 0 doesn't change the value,so remove it from the expression
y=−1
y=21y=−1
Solution
y1=−1,y2=21
Show Solution