Question

Factorise a^2 - a -72

Answer 1

$\bigstar\bf\blue{ANSWER}\bigstar$

$\bigstar\rm\red{GIVEN}\bigstar$

• Factorise $\rm{a^{2}-a-72}$

$\bigstar\rm\red{METHOD\:USED}\bigstar$

• Splitting the middle term.

• we have to sllit the variable in such a way that the Variable term be "p" and costant term "q" Came p×q=72 and p+q=1/a.

Now,

$\implies\rm\red{a^{2}-a-72}$

$\implies\rm\red{a^{2}-9a+8a-72}$

$\implies\rm\red{a(a-9)+8(a-9)}$

$\implies\rm\red{(a+8)(a-9)}$

Thus,The factors are (a+8)(a-9)

$\bigstar\rm\red{MORE\:TO\:KNOW}\bigstar$

• $\rm{(a+b)^2=a^2+b^2+2ab}$

• $\rm{(a-b)^2=a^2+b^2-2ab}$