How would you do a²+2ab-15b²?

Question

The ab confuses me in the second term.

Answer 1

Are you trying to factor it ?  

(a + 5b) (a - 3b)

Now if you FOIL to check it, it works !

Good luck to you !

Answer 2

this is just like any other polynomial. for example:

(x-2)(x-2) = x² -2x-2x +16 = x² -4x +16

we are used to seeing a²+2ab+b². in this case a=x and b=-2 so 2ab is 2(x)(-2) which is the middle term (-4x). so don't let it confuse you.

let's continue with the substitution and rewrite this equation:

x² +2(x)(-2) -15(-2)²

x²-4x -15(4)

x² -4x-60

now let's factor:

(x+6)(x-10)

remember that x=a and -2=b

so the factors are (a-3b)(a+5b)

Answer 3

(a + 5b)(a -3b)

not sure if thats what your looking for

Answer 4

just do (b^2)*[(a/b)^2+2(a/b)-15]

now assume a/b is some x

(b^2)*(x^2+2x-15)=0   now its not dat onfusing

=>x^2+2x-15=0

=>(x+5)*(x-3)=0

=>x=-5  or x=3

=>a/b=5   or a/b=3

Answer 5

a+5b(a-3b)

Answer 6

(a + 5b)(a - 3b)