1. (4x+5y)(2x-3y)+3xy= 4x*2x-4x*3y+5y*2x-5y*3y+3xy=8x^2-12xy+10xy-15y^2+3xy= 8x^2+xy-15y^2
2. (2x^2+3)(4x+5)-8x(x^2-2)=2x^2*4x+2x^2*5+3*4x+3*5-8x*x^2+8x*2=
=8x^3+10x^2+12x+15-8x^3+16x=
=10x^2+28x+15
LHS ⇒ RHS:
Identities:
[1] cos(2A) = 2cos²(A) - 1 = 1 - 2sin²(A)
[2] sin(2A) = 2sin(A)cos(A)
[3] sin(A + B) = sin(A)cos(B) + cos(A)sin(B)
[4] cos(A + B) = cos(A)cos(B) - sin(A)sin(B)
cos(x) - cos(x + 2Θ)
= cos(x) - (cos(x)cos(2Θ) - sin(x)sin(2Θ)) [4]
= cos(x) - cos(x)(1 - 2sin²(Θ)) + sin(x)(2sin(Θ)cos(Θ)) [1] [2]
= cos(x) - cos(x) + 2sin²(Θ)cos(x) + 2sin(Θ)sin(x)cos(Θ)
= 2sin²(Θ)cos(x) + 2sin(Θ)sin(x)cos(Θ)
= 2sin(Θ)(sin(Θ)cos(x) + sin(x)cos(Θ))
= 2sin(Θ)sin(x + Θ)
A scatter plot that has no correlation shows points that a trend line cannot be drawn through and that their is no correlation between the X values and Y values. A scatter plot with a negative correlation has a correlation between the X and y values where as X increases why decreases. A trend line with a negative slope can also be drawn on a negative correlation scatter plot.
Hope that helped or even made sense
