Exploring Algebraic Identities | Exercise 4.4

Question 1

Fill in the blanks to complete the following identities:

Question diagram 1
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Solution

We will factorize each given quadratic expression into its binomial factors.

Step 1 — Factorize s211s+24s^2 - 11s + 24

We need two numbers. Their product must be 24. Their sum must be -11. These numbers are -3 and -8.

s211s+24s^2 - 11s + 24

=s23s8s+24= s^2 - 3s - 8s + 24

=s(s3)8(s3)= s(s - 3) - 8(s - 3)

(s3)(s8)\boxed{(s - 3)(s - 8)}

Diagram 1

Step 2 — Find the missing factor for (x+1)(x + 1)

We need to factor the expression 3x24x73x^2 - 4x - 7. We look for two numbers. Their product must be 3×7=-213 \times -7 = \textbf{-21}. Their sum must be -4. These numbers are -7 and 3.

3x24x73x^2 - 4x - 7

=3x27x+3x7= 3x^2 - 7x + 3x - 7

=x(3x7)+1(3x7)= x(3x - 7) + 1(3x - 7)

(3x7)(x+1)\boxed{(3x - 7)(x + 1)}

Diagram 2

Step 3 — Find the missing terms for 10x211x610x^2 - 11x - 6

We need to factor the expression 10x211x610x^2 - 11x - 6. We look for two numbers. Their product must be 10×6=-6010 \times -6 = \textbf{-60}. Their sum must be -11. These numbers are -15 and 4.

10x211x610x^2 - 11x - 6

=10x215x+4x6= 10x^2 - 15x + 4x - 6

=5x(2x3)+2(2x3)= 5x(2x - 3) + 2(2x - 3)

(2x3)(5x+2)\boxed{(2x - 3)(5x + 2)}

Diagram 3

Step 4 — Factorize 6x2+7x+26x^2 + 7x + 2

We need two numbers. Their product must be 6×2=126 \times 2 = \textbf{12}. Their sum must be 7. These numbers are 3 and 4.

6x2+7x+26x^2 + 7x + 2

=6x2+3x+4x+2= 6x^2 + 3x + 4x + 2

=3x(2x+1)+2(2x+1)= 3x(2x + 1) + 2(2x + 1)

(3x+2)(2x+1)\boxed{(3x + 2)(2x + 1)}

Diagram 4

Answer

(i) s211s+24=(s3)(s8)s^2 - 11s + 24 = (s - 3)(s - 8) (ii) (3x7)(x+1)=(3x24x7)(3x - 7)(x + 1) = (3x^2 - 4x - 7) (iii) 10x211x6=(2x3)(5x+2)10x^2 - 11x - 6 = (2x - 3)(5x + 2) (iv) 6x2+7x+2=(3x+2)(2x+1)6x^2 + 7x + 2 = (3x + 2)(2x + 1)

More questions in Exercise 4.4

Q1

Fill in the blanks to complete the following identities:

Q2

Select and use the identity that will help you find the following products without multiplying directly:

(i) (41)2(41)^2

(ii) (27)2(27)^2

(iii) (23×17)(23 \times 17)

(iv) (135)2(135)^2

(v) (97)2(97)^2

(vi) (18×29)(18 \times 29)

(vii) (34×43)(34 \times 43)

(viii) (205)2(205)^2

Q3

Factor the following:

(i) 9a2+b2+4c26ab+12ac4bc9a^2 + b^2 + 4c^2 - 6ab + 12ac - 4bc

(ii) 16s2+25t240st16s^2 + 25t^2 - 40st

(iii) r2r42r^2 - r - 42

(iv) 49g2+14gh+h249g^2 + 14gh + h^2

(v) 64u2+121v2+4w2176uv32uw+44vw64u^2 + 121v^2 + 4w^2 - 176uv - 32uw + 44vw

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