[tex]\left(a\left(a+b\right)-b\left(a+b\right)\right)
[/tex] We take: [tex]a\left(a+b\right)[/tex] And aply the law of the exponents: [tex]=a^2+ab[/tex] we do the same process at the other side and we get: [tex]=a^2+ab-ab-b^2[/tex] Now: [tex]+ab-ab=0[/tex] So we get that: [tex]=a^2-b^2[/tex]
