1.

Expand (x – a)(x – b). If x2 – 7x + 12 = (x – a)(x – b) then find a + b.Also find ab Calculate the values of a, b. Write the factors of (x2 – 7x +12 ). Find the solutions of (x2 – 7x + 12).

Answer»

(x – a) (x – b) = x2 – bx – ax + ab

= x2 – x (a + b) + ab

= x2 – 7x + 12 = (x – a)(x – b)

a + b = 7

ab = 12

(a + b)2 – 4ab = 72 – 4 x 12 = 49 – 48 = 1 = a – b

a + b = 7

a – b = 1, 2a = 8 a = 8/2 = 4

b = 7 – 4 = 3 a = 4 and b = 3.

Solution of x2 – 7x + 12 is x2 – 7x + 12 = (x – 4) (x – 3)

Solutions = 4, 3



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