Use the identity $(x + a) (x + b) = x^{2} + (a + b) x + a b$ to find the following product.
$(4 x + 5) (4 x - 1)$

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Solution

Finding the product:
Using the identity $(x + a) (x + b) = x^{2} + (a + b) x + a b$
$(4 x + 5) \times (4 x - 1) = {(4 x)}^{2} + (5 - 1) \times (4 x) + 5 \times (- 1) = 16 x^{2} + 4 \times (4 x) + (- 5) = 16 x^{2} + 16 x - 5$
Hence, $(4 x + 5) (4 x - 1) = 16 x^{2} + 16 x - 5$ .

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Question 2(iv)
Use the identity $(x + a) (x + b) = x^{2} + (a + b) x + a b$ to find the following products:
$(4 x + 5) (4 x - 1)$

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