Identify quadratic trinomial form: Identify the quadratic trinomial and its form.The given expression is 4x2−28x+40. This is a quadratic trinomial of the form ax2+bx+c.
Find two numbers for multiplication and addition: Find two numbers that multiply to ac (the product of the coefficient of x2 and the constant term) and add up to b (the coefficient of x).For the given expression, a=4, b=−28, and c=40. We need to find two numbers that multiply to 4×40=160 and add up to −28.
Find the two numbers: Find the two numbers.The two numbers that multiply to 160 and add up to −28 are −20 and −8.Check: (−20)×(−8)=160 and (−20)+(−8)=−28.
Rewrite middle term using two numbers: Rewrite the middle term using the two numbers found in Step 3.Rewrite −28x as −20x−8x.The expression now looks like this: 4x2−20x−8x+40.
Factor by grouping: Factor by grouping.Group the terms into two pairs: (4x2−20x) and (−8x+40).Factor out the greatest common factor from each pair.From the first pair, factor out 4x: 4x(x−5).From the second pair, factor out −8: −8(x−5).The expression now looks like this: 4x(x−5)−8(x−5).
Factor out common binomial factor: Factor out the common binomial factor.The common binomial factor is (x−5).Factor this out to get: (x−5)(4x−8).
Simplify second factor: Simplify the second factor if possible.The second factor 4x−8 can be further factored by taking out the common factor of 4.This gives us: 4(x−2).
Write final factored form: Write the final factored form of the expression.The final factored form of the expression is (x−5)(4)(x−2).