Question:
Factorised form of r2 – 10r + 21 is
(a) (r – 1) (r – 4)
(b) (r – 7) (r – 3)
(c) (r – 7) (r + 3)
(d) (r + 7) (r + 3)
Solution:
(b) (r – 7) (r – 3)
Factorised form of r2 – 10r + 21 is = r2 – 7r – 3r + 21
Take out the common factors,
= r (r – 7) – 3 (r – 7)
Again take out the common factor,
= (r – 7) (r – 3)
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