#3**0 **

You didn't answer my question:)

should it be 1.6x ?

I'll assume it should

x^2+1.6x-4.2=0

How about times both sides by 10 and see if that helps.

$$10x^2+16x-42=0$$

I think I will divide everthing by 2

$$5x^2+8x-21=0$$

I am looking for 2 numbers that multiply to -5*21 that is -105 and add to 8

Since the multply to a negative, one is neg and the other is pos.

Since they add to a positive, the bigger one will be the positive one.

some of The factors of 105 are 5,7,3, and 15-7=8

So the numbers are +15 and -7

Now i am going to replace 8x with 15x-7x

$$5x^2+15x-7x-21=0$$

Now factorise in pairs

$$\\5x(x+3)-7(x+3)=0\\

(5x-7)(x+3)=0$$

So either 5x-7=0 or x+3=0

so 5x =7 or x=-3

so **x=7/5 or x=-3**

do you know how to finish it?

It would have been easier just to use the quadratic formula with the original equation LOL :)

I thought you were suppose to do it by factorising - that is why I did it this 'hard' way.

Melody
Jan 11, 2015