Multiplying by a conjugate gives a rational number because (a + b)(a - b.=

Use foil.

(a+b)(a–b)
a^2 -ab +ab -b^2
a^2 – b^2

Hope I helped :)

I’m pretty sure the * means multiplication. so, if you multiply 5*1, it would equal 5. they are basically are-writing 5x1 as 5*1. so they would be… 5 10152025303540455055