m^2+2m-3=(m^2+2*1*m+1)-1-3=(m+1)^2-4=(m+1)^2-2^2=(m+1-2)(m+1+2)=(m-1)(m+3)
m^2+4m-5=(m^2+2*2*m+4)-4-5=(m+2)^2-9=(m+2)^2-3^2=(m+2-3)(m+2+3)=(m-1)(m+5)
y^2+4y+3=(y^2+2*2*y+4)-4+3=(y+2)^2-1=(y+2)^2-1^2=(y+2-1)(y+2+1)=(y-1)(y+3)
x^2+3x+2=(x^2+2x+1)+x+1=(x+1)^2+(x+1)=(x+1)(x+1+1)=(x+1)(x+2)