Algebra
Calculus
Trigonometry
Matrix
Question
Factor the expression
(x−7)(x+3)
Evaluate
x2−4x−21
Rewrite the expression
x2+(3−7)x−21
Calculate
x2+3x−7x−21
Rewrite the expression
x×x+x×3−7x−7×3
Factor out x from the expression
x(x+3)−7x−7×3
Factor out −7 from the expression
x(x+3)−7(x+3)
Solution
(x−7)(x+3)
Show Solution
Find the roots
x1=−3,x2=7
Evaluate
x2−4x−21
To find the roots of the expression,set the expression equal to 0
x2−4x−21=0
Factor the expression
More Steps
Evaluate
x2−4x−21
Rewrite the expression
x2+(3−7)x−21
Calculate
x2+3x−7x−21
Rewrite the expression
x×x+x×3−7x−7×3
Factor out x from the expression
x(x+3)−7x−7×3
Factor out −7 from the expression
x(x+3)−7(x+3)
Factor out x+3 from the expression
(x−7)(x+3)
(x−7)(x+3)=0
When the product of factors equals 0,at least one factor is 0
x−7=0x+3=0
Solve the equation for x
More Steps
Evaluate
x−7=0
Move the constant to the right-hand side and change its sign
x=0+7
Removing 0 doesn't change the value,so remove it from the expression
x=7
x=7x+3=0
Solve the equation for x
More Steps
Evaluate
x+3=0
Move the constant to the right-hand side and change its sign
x=0−3
Removing 0 doesn't change the value,so remove it from the expression
x=−3
x=7x=−3
Solution
x1=−3,x2=7
Show Solution