Factorise the following:

(x + 3)(3x - 4)

Step-by-step explanation:

Given

3x² + 5x - 12

Consider the factors of the product of the coefficient of the x² term and the constant term which sum to give the coefficient of the x- term.

product = 3 × - 12 = - 36 and sum = + 5

The factors are + 9 and - 4

Use these factors to split the x- term

3x² + 9x - 4x - 12 ( factor first/second and third/fourth terms )

= 3x(x + 3) - 4(x + 3) ← factor out (x + 3) from each term

= (x + 3)(3x - 4)

Thus

3x² + 5x - 12 = (x + 3)(3x - 4) ← in factored form

the value of v.w= -12.

step-by-step explanation:

we are given three vector r,v and w as:

r = < 5, -5, -2> ; v = < 2, -8, -8> ; w = < -2, 6, -5>

we know that r,v and w could also be represented as:

r=5i-5j-2k

v=2i-8j-8k

and w= -2i+6j-5k

where i,j and k are the unit vectors of x,y and z-axis respectively.

also we know that it has the following property:

i.i=1 ; j.j=1; k.k=1

and i.=j.i=i.k=k.i=j.k=k.j=0

i.e. when we multiply two vectors or we find it's dot product we need to only multiply the components of x coordinates with each other; y with each other and z with each other.

hence, v.w= (2i-8j- -2i+6j-5k)

                  = 2×(-2)+(-8)×(6)+(-8)×(-5)

                  = -4-48+40

                  = -12

hence, v.w= -12

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