F2 Ch3 Identities

Which of the following is an identity?

• x(x + y) = x² + y

• (x – 1)(x + 2) = x² + x + 2

• (x – y)² = (y – x)²

If 3x² + Ax + 12 ≡ (3x – 4)(x + B), where A and B are constants, then

• A. A = 13 and B = 3.

• B. A = 13 and B = –3.

• C. A = –13 and B = 3.

• D. A = –13 and B = –3.

If x² + Ax – 15 ≡ (x + B)(x + C), where A, B and C are integral constants, which of the following can be the value of A?

I. 14

II. -2

II. -15

• II only

• I and II only

• I and III only

• I, II and III

(−x + 6)(−x − 6) =

• −x² + 36.

• x² − 12x + 36.

• −x² − 36.

• x² − 36.

(x − 3y)² − (x + 3y)² =

• 12xy.

• −12xy.

• 2x² − 18y².

• 2x² + 18y².

(x + y + 2)(x + y − 2) =

• x² + y² + 2xy − 4.

• x² + y² − 2xy + 4.

• x² + y² − 2xy − 4.

• x² + y² + 2xy + 4.

(4x + y)² - (4x - y)² =

• 0.

• 2y².

• 8xy.

• 16xy.

If m and n are constants such that x² + mx + n ≡ (x + 4)(x - m) + 6, then n =

• -8.

• -2.

• 2.

• 6.

If α and β are constants such that (x − 8)(x + α) − 6 ≡ (x − 9)² + β, then β =

• −26.

• −10.

• −7.

• −6.