Question

Simplify: 3x(4x-5)+3 and find its value for a) x=3 b) x=1/2

Answer 1

(a) x = 3

⇒ 3x(4x - 5) + 3

⇒ 3 × 3(4 × 3 - 5) + 3   [put the value of x = 3]

⇒ 9(12-5 )+ 3

⇒ 9 × 7 + 3

⇒ 63 + 3

⇒ 66

Now,

(b)  x = $\bf \frac{1}{2}$

⇒ 3x(4x - 5) + 3

⇒ 3 × $\bf \frac{1}{2}$(4 × $\bf \frac{1}{2}$ - 5) + 3  [pu the value of x = $\bf \frac{1}{2}$]

⇒ $\bf \frac{3}{2}$ (2 - 5) + 3

⇒ $\bf \frac{3}{2}$(-3) + 3

⇒ $\bf \frac{-9}{2}$ + 3

⇒ $\bf \frac{-9 + 6}{2}$

⇒ $\bf \frac{-3}{2}$

Answer 2

(a)x=3

=3x3(4x3-5)+3

=9(12-5)+3

=9x7+3

=63+3

=66

(b)x=1/2

=3x1/2(4x1/2-5)+3

=3/2(2-5)+3

=3/2x(-3)+3

=(-9/2)+3

=(-9+6)/2

=(-3/2)