factorise 4y^3-2y^2-y+3
Answers
Answer:
Step-by-step explanation:
4.1 Pull out like factors :
4y3 - 2y2 - 4y + 2 =
2 • (2y3 - y2 - 2y + 1)
Checking for a perfect cube :
4.2 2y3 - y2 - 2y + 1 is not a perfect cube
Trying to factor by pulling out :
4.3 Factoring: 2y3 - y2 - 2y + 1
Thoughtfully split the expression at hand into groups, each group having two terms :
Group 1: -2y + 1
Group 2: 2y3 - y2
Pull out from each group separately :
Group 1: (-2y + 1) • (1) = (2y - 1) • (-1)
Group 2: (2y - 1) • (y2)
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Add up the two groups :
(2y - 1) • (y2 - 1)
Which is the desired factorization
Trying to factor as a Difference of Squares :
4.4 Factoring: y2 - 1
Theory : A difference of two perfect squares, A2 - B2 can be factored into (A+B) • (A-B)
Proof : (A+B) • (A-B) =
A2 - AB + BA - B2 =
A2 - AB + AB - B2 =
A2 - B2
Note : AB = BA is the commutative property of multiplication.
Note : - AB + AB equals zero and is therefore eliminated from the expression.
Check : 1 is the square of 1
Check : y2 is the square of y1
Factorization is : (y + 1) • (y - 1)
Final result :
2 • (y + 1) • (y - 1) • (2y - 1)
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