Exploring Algebraic Identities | Exercise 4.3

Question 1

Find the following squares using one of the above identities. Determine which of these identities will make these calculations easier.

(i) 1172117^2

(ii) 78278^2

(iii) 1982198^2

(iv) 2142214^2

(v) 110421104^2

(vi) 112021120^2

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Solution

We will use algebraic identities to simplify these square calculations.

Step 1 — Calculate 1172117^2

Let's express 117 as a sum. We can write 117=110+7117 = 110 + 7. We will use the identity (a+b)2=a2+2ab+b2(a + b)^2 = a^2 + 2ab + b^2. Here, a=110a = 110 and b=7b = 7.

1172=(110+7)2117^2 = (110 + 7)^2

=1102+2(110)(7)+72= 110^2 + 2(110)(7) + 7^2

=12100+1540+49= 12100 + 1540 + 49

=13689= 13689

13689\boxed{13689}

Diagram 1

Step 2 — Calculate 78278^2

Let's express 78 as a difference. We can write 78=80278 = 80 - 2. We will use the identity (ab)2=a22ab+b2(a - b)^2 = a^2 - 2ab + b^2. Here, a=80a = 80 and b=2b = 2.

782=(802)278^2 = (80 - 2)^2

=8022(80)(2)+22= 80^2 - 2(80)(2) + 2^2

=6400320+4= 6400 - 320 + 4

=6084= 6084

6084\boxed{6084}

Step 3 — Calculate 1982198^2

Let's express 198 as a difference. We can write 198=2002198 = 200 - 2. We will use the identity (ab)2=a22ab+b2(a - b)^2 = a^2 - 2ab + b^2. Here, a=200a = 200 and b=2b = 2.

1982=(2002)2198^2 = (200 - 2)^2

=20022(200)(2)+22= 200^2 - 2(200)(2) + 2^2

=40000800+4= 40000 - 800 + 4

=39204= 39204

39204\boxed{39204}

Step 4 — Calculate 2142214^2

Let's express 214 as a sum. We can write 214=200+14214 = 200 + 14. We will use the identity (a+b)2=a2+2ab+b2(a + b)^2 = a^2 + 2ab + b^2. Here, a=200a = 200 and b=14b = 14.

2142=(200+14)2214^2 = (200 + 14)^2

=2002+2(200)(14)+142= 200^2 + 2(200)(14) + 14^2

=40000+5600+196= 40000 + 5600 + 196

=45796= 45796

45796\boxed{45796}

Step 5 — Calculate 110421104^2

Let's express 1104 as a sum. We can write 1104=1100+41104 = 1100 + 4. We will use the identity (a+b)2=a2+2ab+b2(a + b)^2 = a^2 + 2ab + b^2. Here, a=1100a = 1100 and b=4b = 4.

11042=(1100+4)21104^2 = (1100 + 4)^2

=11002+2(1100)(4)+42= 1100^2 + 2(1100)(4) + 4^2

=1210000+8800+16= 1210000 + 8800 + 16

=1218816= 1218816

1218816\boxed{1218816}

Step 6 — Calculate 112021120^2

Let's express 1120 as a sum. We can write 1120=1100+201120 = 1100 + 20. We will use the identity (a+b)2=a2+2ab+b2(a + b)^2 = a^2 + 2ab + b^2. Here, a=1100a = 1100 and b=20b = 20.

11202=(1100+20)21120^2 = (1100 + 20)^2

=11002+2(1100)(20)+202= 1100^2 + 2(1100)(20) + 20^2

=1210000+44000+400= 1210000 + 44000 + 400

=1254400= 1254400

1254400\boxed{1254400}

Answer

(i) 1172=13689117^2 = 13689 (ii) 782=608478^2 = 6084 (iii) 1982=39204198^2 = 39204 (iv) 2142=45796214^2 = 45796 (v) 11042=12188161104^2 = 1218816 (vi) 11202=12544001120^2 = 1254400

More questions in Exercise 4.3

Q1

Find the following squares using one of the above identities. Determine which of these identities will make these calculations easier.

(i) 1172117^2

(ii) 78278^2

(iii) 1982198^2

(iv) 2142214^2

(v) 110421104^2

(vi) 112021120^2

Q2

Factor using suitable identities:

(i) 16y224y+916y^2 - 24y + 9

(ii) 94s2+6st+4t2\frac{9}{4}s^2 + 6st + 4t^2

(iii) m29+mk3+k24+3nk+2mn+9n2\frac{m^2}{9} + \frac{mk}{3} + \frac{k^2}{4} + 3nk + 2mn + 9n^2

(iv) p2162+16p2\frac{p^2}{16} - 2 + \frac{16}{p^2}

(v) 9a2+4b2+c212ab+6ac4bc9a^2 + 4b^2 + c^2 - 12ab + 6ac - 4bc

Q3

Expand the following using the identity (a+b+c)2=a2+b2+c2+2ab+2bc+2ca(a + b + c)^2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca:

(i) (p+3q+7r)2(p + 3q + 7r)^2

(ii) (3x2y+4z)2(3x - 2y + 4z)^2

Q4

Is this an identity?

(a+bc)2+(ab+c)2+(abc)2=2a2+2b2+2c2(a + b - c)^2 + (a - b + c)^2 + (a - b - c)^2 = 2a^2 + 2b^2 + 2c^2.

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