Compute these products using the suggested identity. (i) 46² using Identity 1A for (a + b)² Class 8
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Compute these products using the suggested identity. (i) 46² using Identity 1A for (a + b)² Class 8
Question 1.
Compute these products using the suggested identity.
(i) 46² using Identity 1A for (a + b)²
(ii) 397 × 403 using Identity 1C for (a + b) (a - b)
(iii) 91² using Identity IB for (a - b )²
(iv) 43 × 45 using Identity 1C for (a + b) (a -b)
Solution:
(i) 46² = (40 + 6)²
= 40² + 2 × 40 × 6 + 6²
= 1600 + 480 + 36
= 2116.
(ii) 397 × 403 = (400 - 3) (400 + 3)
= 400² - 3²
= 160000 - 9 = 150091.
(iii) 91² = (100 - 9)²
= 100² - 2 × 100 × 9 + 9²
= 10000 - 1800 + 81
= 8281
(iv) 43 × 45 = (44 - 1) (44 + 1) = 44² - 1²
= 1936 - 1 = 1935