Expand simply means multiply and simplify Principle (a+b)(c+d)=a(c+d)+b(c+d) (a−b)(c+d)=a(c+d)−b(c+d) (7r−5)(3r+4)=7r(3r+4)−5(3r+4) 7r(3r+4)−5(3r+4)=7r×3r+7r×4−5×3r−5×4 7r×3r+7r×4−5×3r−5×4=21r2+28r−15r−20 21r2+28r−15r−20=21r2+13r−20 NOTE: r×r=r2 a=a1 From the law of indices, am×an=am+n r×r=r1×r1=r1+1=r2