Question

What's x(x-9)=10?

a) x= 20, x= -2
b )x= 65, x= -56
c) x= -10, x= 1
d) x= 10, x= -1

Answer 1

Expand and put them all on one side in decreasing order of degree of x:
x^2 - 9x - 10 = 0
-9 = 1 - 10
-10 = 1 * (-10)
so (x+1)(x-10) = 0
So
x+1=0
(x= -1)
And
x-10=0
(x=10)
So the solutions are 10 and -1 which is d.

Answer 2

Hi Laysia

x( x - 9) = 10
x² - 9x = 10
x² - 9x - 10 = 0
Factor left side
(x +1)(x-10)
Now we can set the factors equal to 0
x +1 = 0 or x - 10 = 0
x = 0 - 1 or x = 0 + 10
x= - 1 or x = 10

Answer : x - 1 or x = 10

The correct option is : D

Let me know if you have any further questions.