Question

Which equations are correct?

Select each correct answer.



−7x2(4x3+2)=−28x6−14x2
−5d3(3d2+4)=−15d5−20d3
−2b3(6b2+5)=−12b5−10b3
−3y4(5y2+2)=−15y8−6y4

Answer 1

`-5d^3(3d^2+4)=-15d^5-20d^3`

`-2b^3(6b^2+5)=-12b^5-10b^3`

Explanation:

Given equations are correct if the left side and right side of the equation are same,

First option :
`-7x^2(4x^3+2)=(-7x^2)(4x^3)+(-7x^2)(2)`

`=-28x^(2+3)-14x^2`

`=-28x^5-14x^2\\eq -28x^6-14x^2`

Second option :
`-5d^3(3d^2+4)=(-5d^3)(3d^2)+(-5d^3)(4)`

`=-15d^(3+2)-20d^3`

`=-15d^5-20d^3`

Third option :
`-2b^3(6b^2+5)=(-2b^3)(6b^2)+(-2b^3)(5)`

`=-12b^(3+2)-10b^3`

`=-12b^5-10b^3`

Fourth option :
`-3y^4(5y^2+2)=(-3y^4)(5y^2)+(-3y^4)(2)`

`=-15y^(4+2)-6y^4`

`=-15y^6-6y^4\\eq -15y^8-6y^4`