Question

4x² - 25x +21 factorise​

Answer 1

Answer:

$4x^{2} -25x+21\\= 4x2 - 4x - 21x + 21\\=4x(x-1) - 21(x-1)\\=(4x-21)(x-1)\\\\x = 1 or x = 21/4$

Answer 2

ANSWER:

• Factorisation of the above expression is (x-1)(4x-21)

GIVEN:

• P(x) = 4x²-25x+21

TO FIND:

• Value of the above expression.

SOLUTION:

= 4x²-25x+21

= 4x²-21x-4x+21

= (4x²-4x)+(-21x+21)

= 4x(x-1)-21(x-1)

= (x-1)(4x-21)

Factorisation of the above expression is (x-1)(4x-21)

NOTE:

Some important formulas:

(a+b)² = a²+b²+2ab

(a-b)² = a²+b²-2ab

(a+b)(a-b) = a²-b²

(a+b)³ = a³+b³+3ab(a+b)

(a-b)³ = a³-b³-3ab(a-b)

a³+b³ = (a+b)(a²+b²-ab)

a³-b³ = (a-b)(a²+b²+ab)

(a+b)² = (a-b)²+4ab

(a-b)² = (a+b)²-4ab