Question

30 points! please help!

Answer 1

Answer:

Step-by-step explanation:

Answer 2

Answer:

Therefore

15.

$25c^{2}-9$

16.

$(y+8)(y+1)$

17.

$(x-3y)(x-7y)$

Step-by-step explanation:

15.

$(5c^{2} +3)(5c^{2}-3)$

Using the Identity (a + b)(a - b) = (a² - b²) we get

Consider here a = 5c and b = 3 then we will have

$((5c)^{2} -(3)^{2})=25c^{2}-9$    .....as required

16.

$y^{2}+9y+8$

Here Factorize 8 such that sum up to be 9

∴ 8 × 1  = 8 and 8 + 1 =9

$y^{2}+9y+8\\y^{2}+8y+y+8\\y(y+8)+1(y+8)\\(y+8)(y+1)$ ... as required

17.

$x^{2}-10xy+21y^{2}$

Here Factorize 21 such that sum up to be -10

∴ -3 × -7  = + 21 and -3 - 7 = - 10

$x^{2}-10xy+21y^{2}\\x^{2}-3xy-7xy+21y^{2}\\x(x-3y)-7y(x-3y)\\(x-3y)(x-7y)$ ........as required

Therefore

15.

$25c^{2}-9$

16.

$(y+8)(y+1)$

17.

$(x-3y)(x-7y)$