Question

Solve the following quadratic equations by factorisation.

i. 7m² = 21 m 

ii. m² – 11 = 0

Answer 1

i. 7m² = 21m 

∴ 7m² – 21m = 0 

∴ m² – 3m = 0 …[Dividing both sides by 7] 

∴ m(m – 3) = 0

By using the property, if the product of two numbers is zero, then at least one of them is zero, we get

∴ m = 0 or m – 3 = 0 

∴ m = 0 or m = 3

∴ The roots of the given quadratic equation are 0 and 3.

ii.

By using the property, if the product of two numbers is zero, then at least one of them is zero, we get

∴ m + √11 = 0 or m – √11 = 0

∴ m = -√11 or m = √11

∴ The roots of the given quadratic equation are –

√11 and √11.