Question

5 - Se x = (b + c)2e y = (2b - 3c).(2b +
3c), então o valor de x - y é:
a a
do
a) 10b2-3c
b) 2b2 - 3c2 + bc
c) 3b? + 2c2-bc
d) -10b2 + 3c2 + 2bc
e) 10b2 - 3c2 + 2bc​

Answer 1

Resposta:

$x = (b + c) {}^{2} \\ \\ x = {b}^{2} + 2bc + {c}^{2} \\ \\ y = (2b - 3c)(2b + 3c) \\ \\ y = (2b) {}^{2} - ({3c})^{2} \\ \\ y = 4 {b}^{2} - 9 {c}^{2} \\ \\ x - y = {b}^{2} + 2bc + {c}^{2} - (4 {b}^{2} - 9 {c}^{2} ) \\ \\ x - y = {b}^{2} + 2bc + {c}^{2} - 4 {b}^{2} + 9 {c}^{2} \\ \\ x - y = - 3 {b}^{2} + 10 {c}^{2} + 2bc$