Question

Help please

Factorise

x²-x-56

its due in 4 minutes

Answer 1

x^2-x-56

Think of two numbers that will equal to -x and -56.

Use the 7 and 8 times table.

(x-8)(x+7)

Because - negative number * + positive number= - negative number

(x-8)(x+7)= 0

x-8= 0

Move -8 to the other side. Sign changes from -8 to +8.

x-8+8= 0+8

x= 8

x+7= 0

Move +7 to the other side. Sign changes from +7 to -7.

x+7-7= 0-7

x= -7

Answers:

x= 8 , x= -7

Answer 2

(x-8)(x+7)

Explanation:

using quadratic formula we have

x=
`\frac{-b+-\sqrt{b^(2)-4*a*c}}{2*a}`

we have:

x^2-x-56=0

a= 1 b=-1 c=-56

so we have:

x=(-(-1)+-sqrt(1^1-4*(1)*(-56)))/(2*1)

x=1+-sqrt(1-4*(-56))/(2)

x=(1+-sqrt(225))/2

x=(1+-15)/2

so we have the roots:

x1=(1+15)/2 =8

x2=(1-15)/2=-7

so the answer is (x-8)(x+7)