Question

Hello there I need help with this equation
A factor of x^{2} + 4x -5

Answer 1

To get something of that form, we need
\[(x-a)(x+b) = x(x+b)-a(x+b) = x^2 + bx - ax -ab\]\[=x^2 + (b-a)x - ab\]Comparing with your equation, that means
\[b-a = 4\]\[-a*b=-5\]Can you think of two numbers which make that true? The numbers must multiply to -5, and add to +4.

Answer 2

Hopefully it is obvious that one is negative and one is positive :-)

Answer 3

Hello and thank you for replying :o)
anyway I do not understand how you started to solve the equation

Answer 4

the answers are
a)x+5
b)x-5
c)x+1
d)x-20
e)x+20

Answer 5

so would it be answer b?

Answer 6

To get \[x^2+4x-5\]we need the factors of 5, which are 1 and 5. We have 4 choices:
\[(x+1)(x+5)\]\[(x-1)(x+5)\]\[(x+1)(x-5)\]\[(x-1)(x-5)\]
Now, which of those expands to \(x^2+4x-5\)?

Hint: the signs need to be 1 positive and 1 negative, because they get multiplied together to make -5. And the middle terms add together to give +4x.

Answer 7

so it would be
1+5
-1+5
1-5
-1-5

Answer 8

\[(x+1)(x+5) = x^2 + 5x +1x+ 5\]\[(x-1)(x+5) = x^2 + 5x - 1x -5\]\[(x+1)(x-5) = x^2-5x+1x-5\]\[(x-1)(x-5) =x^2-5x-1x+5\]
which of those is the right one?

Answer 9

the second

Answer 10

is that right?

Answer 11

yes, \((x-1)(x+5) = x^2+5x-1x-5 = x^2+4x-5\) so it would appear that A) (x+5) is the answer you want.

Answer 12

Thank you very much Whpalmer4 thank you very much