Algebra
Calculus
Trigonometry
Matrix
Question
Factor the expression
(a−5)(a+4)
Evaluate
a2−a−20
Rewrite the expression
a2+(4−5)a−20
Calculate
a2+4a−5a−20
Rewrite the expression
a×a+a×4−5a−5×4
Factor out a from the expression
a(a+4)−5a−5×4
Factor out −5 from the expression
a(a+4)−5(a+4)
Solution
(a−5)(a+4)
Show Solution
Find the roots
a1=−4,a2=5
Evaluate
a2−a−20
To find the roots of the expression,set the expression equal to 0
a2−a−20=0
Factor the expression
More Steps
Evaluate
a2−a−20
Rewrite the expression
a2+(4−5)a−20
Calculate
a2+4a−5a−20
Rewrite the expression
a×a+a×4−5a−5×4
Factor out a from the expression
a(a+4)−5a−5×4
Factor out −5 from the expression
a(a+4)−5(a+4)
Factor out a+4 from the expression
(a−5)(a+4)
(a−5)(a+4)=0
When the product of factors equals 0,at least one factor is 0
a−5=0a+4=0
Solve the equation for a
More Steps
Evaluate
a−5=0
Move the constant to the right-hand side and change its sign
a=0+5
Removing 0 doesn't change the value,so remove it from the expression
a=5
a=5a+4=0
Solve the equation for a
More Steps
Evaluate
a+4=0
Move the constant to the right-hand side and change its sign
a=0−4
Removing 0 doesn't change the value,so remove it from the expression
a=−4
a=5a=−4
Solution
a1=−4,a2=5
Show Solution