Question

Simplify 6a (2a²-5) + 2a² (3a + 5) when a = (-1/2)

Answer 1

$\huge\mathfrak\pink{Answer\:is\:14.5}$

we have

6 a(2a^2-5)+2a^2(3a+5)

= 12 a^3-30 a + 6 a^3+10 a^2

= 18 a^3+10 a^2-30 a

now substitute a = -1/2

= 18×(-1)/8+10/4 - 30(-1)/2

= - 9/4+5/2+15

= -2.25 + 1.5 + 15

= -2.25 + 16.5

= 14.5