Question

Q15 Factorise: 4x2+8x-5
a) (2x-5)(2x+1)
O b) (2x-5)(2x-1)
c) (2x+5)(2x-1)
O d) none of these​

Answer 1

ANSWER:

• Correct option = 'C' i.e (2x+5)(2x-1)

GIVEN:

• P(x)= 4x²+8x-5

TO FIND:

• factorise the above expression.

SOLUTION:

= 4x²+8x-5

= 4x²+10x-2x-5

= 2x(2x+5)-1(2x+5)

= (2x+5)(2x-1)

Correct option = 'C' i.e (2x+5)(2x-1)

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