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45 votes
45 votes
Hello people ~
factorise: y² - 2y - 15​

User Zuodian Hu
by
3.3k points

2 Answers

17 votes
17 votes

Answer:


(y+3)(y-5)

Explanation:

Given the following equation:


y^2-2y-15

To factor any equation, we must first break the equation into different groups and then factor out common terms in till we reach our solution.


y^2-2y-15

(y^2+3y)+(-5y-15)

y^2=yy=y(y+3)

y(y+3)+(-5y-15)

(-5y-15)=-5(y-15)

y(y+3)+-5(y-15)

15/5=3

y\left(y+3\right)-5\left(y+3\right)

y\left(y+3\right)-5\left(y+3\right)=(y+3)(y-5)

=(y+3)(y-5)

Your answer is "(y + 3)(y - 5)."

Hope this helps.

User MrKobayashi
by
2.9k points
23 votes
23 votes

Answer:


(y-5)(y+3)

Explanation:

To factorize
y^2-2y-15


\textsf{for} \ ax^2+bx+c \ \textsf{find} \ v, w \ \textsf{such that} \ v \cdot w=a \cdot c \ \textsf{and} \ v+w=b\\ \textsf{ and group into} \ (ax^2+vx)+(wx+c)


a \cdot c=1 \cdot -15=-15


b=-2

Therefore, the 2 numbers that multiply together to give -15 and add together to give -2 are: -5 and 3


\implies y^2-5y+3y-15


\implies (y^2-5y)+(3y-15)

Factor the parentheses:


\implies y(y-5)+3(y-5)

Factor out the common term
(y-5):


\implies (y-5)(y+3)

User Mikeweather
by
3.1k points