Question

9.- (9a – 7)² =
10.- (5a + 6)² =
11.- (1 + b)² =
12.- (5 – x)² =
13.- (5y² – 3)² =
14.- (7+ y)² =

Answer 1

Respuesta:

9.- (9a – 7)² =

$=\left(9a\right)^2-2\cdot \:9a\cdot \:7+7^2\\\\=81a^2-126a+49$

10.- (5a + 6)² =

$=\left(5a\right)^2+2\cdot \:5a\cdot \:6+6^2\\\\=25a^2+60a+36$

11.- (1 + b)² =

$=1^2+2\cdot \:1\cdot \:b+b^2\\\\=1+2b+b^2$

12.- (5 – x)² =

$=5^2-2\cdot \:5x+x^2\\\\=25-10x+x^2\\\\=x^2-10x+25$

13.- (5y² – 3)² =

$=\left(5y^2\right)^2-2\cdot \:5y^2\cdot \:3+3^2\\\\=25y^4-30y^2+9$

14.- (7+ y)² =

$=7^2+2\cdot \:7y+y^2\\\\=49+14y+y^2\\\\=y^2+14y+49$